Hey, if you don't even know how important DBs are to you, it's probably a good idea to buy a 300# barbell set before anything else. That way you have all the equipment you need to get in the habit of lifting.
After you make sure it's something you want to stick with, then shell out the rest of the money for everything else.
And yes, DBs are helpful, but no, they're not essential.
As they say everywhere else on the site: pick up heavy stuff, eat, and sleep. Don't overthink or overplan unless you are also actively working out. This is not a mental game.
And check craig's list.