#1
does this thing really let you customize your tone a lot/

I really want one because I want to try and find my own guitar tone, and I was wondering how much you could really do with this.

will it make amps sound a little better than they are also/
Guitars:
Ibanez RG350EX
ESP/LTD EC400AT

Soon to have an Ibanez RG1550M, 350M, and RG2610!!
#2
Well it's an EQ, so it's not going to do miracles. But if you're not happy with the range on your amp, like you've already got the mids pegged and want more, they can help in that regard. IMO they can be useful to have around, but they're not going to dramatically change your tone, just let you fine tune it for different situations. I'd suggest looking for a used Danelectro Fish N Chips EQ - they're dirt cheap, work well, and would let you get a feel for them without any major spending.
#3
It helps to shape your tone and can really kick your amp into the next level. If your amps not bassy enough, you can make it bassy enough. If the midrange isn't quite up to par, you can tweak that as well.

If you're not sure, buy a Dano fish and chips eq as it's cheaper and would probably suit you well if you were looking to mess with an EQ in your setup.