Thebeastiworship

basic backup server, low bandwidth router, think client, video playback/web browsing machine.

Technically, yes. Up until 2 weeks ago, I was running Debian Linux on a PowerPC based Mac Mini from 2004 that happily ran a small web server + transmission torrent client 24/7/365 for 4 years. (minus power outages, of course) Your Dell laptop can probably do it just fine, assuming it can run Linux decently enough, but I definitely would NOT recommend using WiFi for this - plug in to ethernet.

About a raspberry pi.

I was looking into used i7 3770s planning on buying one in the beginning of 2020. Additional RAM is on my plans for this year, I will do a research on SSD prices and plan on getting one. Thanks for the advice I'll really look into it! 

You have a locked CPU so overclocking isn't possible. Although, you could drop in a better processor if you can stumble upon a good deal (preferably an i7-3770, Intel Xeon E3-1230, Intel Xeon E3-1245. Even a locked Sandy would be an improvement like an i7-2600.) This should alleviate bottlenecking compared to your current CPU.
 
On to the video card. Your best bet is either a Used RX 470, 480, 570, 580 or a new RX 570. Additionally, a used GTX 1060 is a good option too. 
 
Also, somethings to consider. An additional 8GB of memory and an SSD would supremely breath new life into your machine. Especially with current pricing right now on memory and storage being as great as ever.

I'll keep that in mind. Thanks again!

1050 ti will be a great pair, although I'd recommend getting something better if you're planning on upgrading your platform (CPU, motherboard, RAM) eventually.
 
A 1660ti would only bottleneck about 20% on your i5, and it's a great 1080p/60fps ultra settings card for once you upgrade your platform