I'm trying to create a good competitive team.
as i recalled i only need 1 member with the keyword for everyone 100 points, so let's say in a 300 point team, i need 3 members with Gotham city keyword and it'll be themed.

i started with
BN atom - 65 as the healer
AA Question - 37 outwitter
BatB Bruce Wayne AE - 48 - outwitter then Batman for that late game whooping!
AA Robin - 66
=216
as far as i'm concerned it's already themed with 3 gotham city keywords.
I think outwit is probably a key into winning games as this is the best way of beating opponents with impervious and damage reducing abilities, since i don't have very many characters that do big damage.
I'm looking at maybe

Cr Nightwing + Lunge to total it up to 300
or maybe Cr Batgirl and have a bit more feats included.

i don't really have much decent figures, but i'll list a few random ones that i think can put up a fight
BatB Jason Blood AE with Etrigan
JL Batman ots
AA Calculator
Cr Robin
BatB wonder woman
BatB superman
really should get clark kent and diana prince though :/
AA Captain Gordon
AA Batman Beyond

what do you guys think?

You missed an important part: All figures on the force needs to have the keyword in order to get theme team benefits.
The "1 per 100" bit is just a minimum requirement to the number of characters you need on the force in order to get the bonuses - for instance Iron Man/War Machine cannot be considered a theme team on their own.
If you want a healer with the Gotham City keyword there is always Alpha Alfred though.

oh really? i didn't know that..
thanks for the info.

A team that might be worth trying out with the figures you have:
JL Batman 75
Crisis Batgirl 70
AA Robin 66
AA Captain Gordon 50
AA Question 37
298 points, with a lot of good support powers. Primarily a close combat brawler team.