Societies are usually fairly cheap - I agree with your therapist.
You can either:
- Join a big society (e.g. RockSoc / Your Course Society / LGBT / Quidditch Society / etc). This way, you have plenty of ops for making friends, but can slip away easily.
- Join a small society (e.g. Ten Pin Bowling / Fencing / etc). This way, you are less likely to be left out, the whole group is one friend group, but you are more likely to be noticed if you don't turn up (and may get messaged asking why / etc).