If you decide to go this route, the kits from Harley Benton are a no-brainer. If you like fuzz, something with humbuckers might suit your needs.
And learning how to do a proper setup is as important as building the kit itself (if not more), so if you don't have it, you will need to get something to measure your string action, I use a machinist ruler, but there are also action gauges that make the job easy. You will also need a capo and feeler gauges to measure the neck relief.
Everything else like screwdrivers and Allen wrenches are something that you probably already have and as I said there are plenty tutorials on how to use all of these tools for a setup.
With a small investment you'll be able to adjust all of your instruments, making them more comfortable to play and allowing you to play for longer periods without fatigue.

The next step, as I said, would be doing a basic fretwork. That is going to bring your guitar to an even higher level, but that is a process that if done wrong can ruin your instrument, so if you don't have a lot of experience working on guitars I'd wait until you can at least do a setup with ease.