I have an epiphone thunderbird and this is the first time Ive ever replaced my strings so I dont have a clue which ones I need.

A friend recomendded getting rotosound strings, but I still dont know what size or gauge or that sort of thing I need.

So can anyone help me with the make of strings I should get or more importantly what size and stuff I need for my bass.

you need BASS strings......

sorry for the wise-crack answer.....what style are you playing? what kind so sound do you want? do you like heavier strings or lighter strings? If you're playing rock, typically some sort of medium gauge round wound fits the bill...

Typically, basses are strung with medium guage, or something similar to 45-65-85-105. Medium is safe. It's all preference. If you like them fatter, get a heavy guage. Skinnier, get a lighter guage. Do you want to keep roundwounds or try some flats? Steel or nickel? As far as brands go, there is plenty of info on TB on the merits of any particular strings. Just remember, once you string it up, intonate as well as tune it. And if you are using a set with different tension, you might need to adjust your trussrod slightly.