Set everything to low, turn on multi-core setting in settings, lower screen resolution one important thing close background applications which may be consuming extra memory.
GTA V 60% discounted on steam, there are other games which are on huge sale. Here are some games which are on many people's wishlist.
Steam Summer Sale 2018
Apart from practising many hours and finding out correct hitboxes, there are other tips that can help you to be a pro. Recently I came across following tips and these really helped me to improve my game.
https://www.killping.com/blog/csgo-pro-tips-tricks/