£200 buy in

Hi! Just a simple question:
what should my bankroll be for a £200 pound buy in cash game?

I’m a student that doesn’t have a lot of cash available so I mainly play “play” chips and micro stakes for practising but a couple of my friends are going for a meet up game in London later this year with buy ins of £200. I’m wondering if it’s worth me even playing with just a single buy in.

Any advice is welcome!