If you have nothing, wait for a basic toolbox to come on sale that includes screwdriver set, hammer, small level, ratchet set, drill bit set, pliers, all that basic stuff (including the box) that gets you started. Then go out and get a nice bit set with adapters and the handy plastic cases they come in.
If you need power tools, a good drill and impact driver set should help. I would look up what brand you want to stick with for a while because then when you buy more tools you can exchange batteries and collect more.
My best used tool to date is a $20 Mastercraft mitre saw used off classifieds. 4 years later, same blade, does the job and I use it a lot. Check classifieds, if you are going to diy you will need drill and a saw of sorts.
You'll soon find you always "need" something else for the job. I like the excuse of buying a new one for the job, but I've been able to get buy borrowing specialty tools just fine too.