Well this is what i did to build my BR from 50$(around 700now),it takes a some time but is worth it cause u dont have to deposit again.
I played 1$sng and mtt untill i got to about a 100$ BR and then moved to 2-3$ sng/mtt,when u get to that level if u managed to cash in 180man or the 90KO youre BR will incress rather quikly and at around 250$ u can start trying the 5$sng/mtt(u can move up quiker but this is just what worked for me)
With that i whouldnt play any NL ring games since the lowest on Full Tilt Poker
is 10NL(obvs. u could buy-in for the min but i whouldnt recament it),if you whant u could play the lowest level limit holdem ring games.
I whould recament atleast 300$ for 10NL but thats just me there are alot of people how start there wit alot lease but im kinda cautios.
Here are some great articles on the matter:
How to Build Your Online Poker Bankroll: Where you Should Start
Good luck and i hope it works out for you.
You just have to find the BRM that suites your playing style and your BR will be going up in no time