Broseephus

Depends on what kind of skills you want to learn. Also I second  the guy that said don't experiment on the office network. That can only end in disaster.
 
If you just want to be able to setup very small home/office networks watch youtube videos explaining the different gear (What is a router? What is a switch? What is a Wireless Access Point?). You don't really need to understand the fundamentals of routing/switching logic to get something like that setup.
 
If you're just doing general IT and want to learn how routers/switches actually work and make decisions on what to do with packets pick up the Comp TIA Network + book and give it a read.
 
If you want to actually get into enterprise level networking pick up Cisco Packet Tracer and some training videos (CBT Nuggets are easy to get into). Even better pick up a Cisco Certification like a CCENT or CCNA.

Some netshell commands can help increase performance in certain applications.
 
For example. In fast paced twitch gaming it is a good idea to disable Nagles Algorithm and certain people may see performance increase by enabling chimney offload depending on their NIC.
There is a method to the madness.
 
 
As far as claiming to 'DOUBLE YOUR INNURNET SPEEDS NAO!'
 
Well yeah that part is either ignorance or trolling.

The primary reason you might want to use different subnets is to keep unnecessary broadcast traffic from reaching every device and isolate the networks from one another. You've chosen a logical way to split them up but you really could just give each subnet a /24 and it will be just as effective and easier to configure/remember.
Here's an example of how I would do it.
10.0.1.0/24 = Main network
10.0.2.0/24 = security camera system
10.0.3.0/24 = Guest network
Basically you would need a router capable of doing the three different networks and a switch that is vlan capable OR you need a layer 3 switch and out some static routes to/from the switch/router

In regards to the DDns service. I would bet the godaddy DDns works on any current version of Windows its typically just a simple application that touches base with a godaddy server periodically, that said I have no personal experience with it and don't know for certain. Also certain router manufacturers will give you a free DDns service (Asus is one that does for certain models). Look through your router settings and see if you have anything in there.

Domain Names are purchased from domain registrars (Godaddy, NameCheap, etc..). They have access to make changes to a database that allows them to register domain names. They pay ICANN and IANA royalites every year for this access and it's not something an individual can feasibly do.
 
Anyway this database is what DNS servers pull information from to stay current on on their DNS records. This is why you can't just use a domain if it's available, because you have no way to control what information DNS servers store. This is also the reason that it's impossible for you to use a domain that someone else is using, because that name is already accounted for in the special database.
 
What you need to do is very simple.
 
Step 1. Purchase a domain name through a domain registrar
Step 2. Through your domain registrar enter the IP address you want the DNS to translate to. You want to use your public IP address from your ISP. http://www.whatsmyip.org/ will give you this information. Your domain registrar will have customer service that can help walk you through this.
Step 3. In your router forward port 80 and whatever other ports you access your server on to your servers local IP address
Step 4. That's it, tell people what the website name is and they can type it into their address bar and go to it.

You can definitely do this and what the ISP doesn't know won't hurt them
 
The best solution is wired but you have to consider the 500 feet from the garage to your grandpas house. You could get around this by either setting up a bridge at the halfway mark (how will you get power to it? keep it enclosed?) or you could use some cheap switches with a fiber uplink port because fiber will go the distance. You may have to settle for wireless connectivity for him (unless he's a gamer-gramps not a big deal)
 
Give us your budget and we'll give you some options.

Domain Names are purchased from domain registrars (Godaddy, NameCheap, etc..). They have access to make changes to a database that allows them to register domain names. They pay ICANN and IANA royalites every year for this access and it's not something an individual can feasibly do.
 
Anyway this database is what DNS servers pull information from to stay current on on their DNS records. This is why you can't just use a domain if it's available, because you have no way to control what information DNS servers store. This is also the reason that it's impossible for you to use a domain that someone else is using, because that name is already accounted for in the special database.
 
What you need to do is very simple.
 
Step 1. Purchase a domain name through a domain registrar
Step 2. Through your domain registrar enter the IP address you want the DNS to translate to. You want to use your public IP address from your ISP. http://www.whatsmyip.org/ will give you this information. Your domain registrar will have customer service that can help walk you through this.
Step 3. In your router forward port 80 and whatever other ports you access your server on to your servers local IP address
Step 4. That's it, tell people what the website name is and they can type it into their address bar and go to it.

I wouldn't experiment on a office network
 
You could just buy a cheapo wireless router and try and set that up at home. Just login the the configuration page (usually 192.168.0.1 or similar) and play with all of the options.

Let's not jump on the DDOS bandwagon here... There is nowhere near enough information to get at that. Secondly just restarting a modem/router will almost always get you the same IP address as the lease hasn't expired. For example my ISP runs lease timers of 30 minutes.

Private Internet Access

Just pray you never need BT tech support. It's like Comcast but with Indians who barely speak english.

Just pray you never need BT tech support. It's like Comcast but with Indians who barely speak english.

Just pray you never need BT tech support. It's like Comcast but with Indians who barely speak english.

Adding a switch will not slow down the network in the slightest unless the switch is performing erratically.
 
Modem > Router > Switch > hosts   is how the internet should flow.

Adding a switch will not slow down the network in the slightest unless the switch is performing erratically.
 
Modem > Router > Switch > hosts   is how the internet should flow.

Prefer to leave your tears away from my networking gear.

Check out Eli The Computer Guy. 
 
Very watchable videos and has a lot of video 'tracks' that will help you learn the core concepts of a subject.
 
He covers both Networking and Server stuff (and a lot more too).

need a L3 switch with ACL support

I use opendns all the time, and have clients using opendns for company web filtering. I have never had a problem with it. Also, opendns will do nothing to effect your ping times, or internet speed (though it may increase/decrease page load times while the dns server responds to your browser with the site's IP address, if your DNS server is really terrible).
 
DNS has nothing to do with much of what you're complaining about anyways.

Oh very nice man. Should do you well. If you get snagged on any of the concepts PM me and I'll do my best to help you out. Good luck!

Alright, first things first. Your switches may have a 10G uplink as an SFP+ port or a standalone ethernet port. But I doubt your 48 port switches are 10G capable across all ports. The may be able to withstand accumulation of such speeds.
 
Anyways, work stations need to be 10G capable as well. If they are not capable, then you need PCI-E cards, and the cheapest I've seen them go for is around $250 per card. Next the cable, CAT 6 is 10G capable but only to a certain lenght meaning you will need CAT 6a or 7 to run it from the rack across the office.
 
Last, switches the only brand I know that make big ethernet based 10G switches is Huawei and CISCO maybe DCN. They have a 48x10G Base-T and in retail it's around $5000, carrier grade of course.
 
So you are looking at an investment of around $10000. Spreading switches over the office may be cheaper/faster however it will be a pain to manage. 
 
And all this is great, until you come to the question do you really need it? I mean 10G is 1000MB/s read/write speeds, and the only way you can achieve this is with a really expensive m.2 SSD or a RAID array.

If network storage is one of the reasons, well let's say 5 people are accessing it simultaneously, over a 10G link. For 5 simultaneous transfers you can get maybe 3-4Gbps per client. If you want more you need to setup link aggregation.

Any time you 'extend' your wifi you are going to lose speed/performance. In fact if you were to have 10 wireless hosts and only one of them connects via the extender and all others connect to the main Access Point (in this case your AC66U). All 10 of the devices are going to take a performance hit. That is the nature of wireless radios my friend.

/24 is only 254 usable IPs 
 
If you want only 16 your best bet is to purchase them from an ISP and then segment your network in a way that if you do need to change providers in the future you can make changes in phases and don't have to do everything at one time to get back up and running.

Just buy any 25 meter long Cat5e or Cat6 cable. Whatever is cheapest.

Went to have a BroLan with my buddy. Was a 3 day session of non stop pc gaming of all different flavors. Spilled beer all over my BRAND NEW keyboard before I had even sat down to use it. Luckily it was before I knew about mechanical so it was only a $40 Sidewinder x4.