Puncture Repair Kits

What's good?
What's bad?
ie if I'm looking for a kit what should I make sure is in it?
Are the kits with compressed air actually useful or are they gimmicky?
Is it better to put together a kit myself? If so with what?
I've spent 2 years riding so far and never had a puncture.
Now I've had 2 in 2 weeks - I figure it's time to get a kit.
ty
What's bad?
ie if I'm looking for a kit what should I make sure is in it?
Are the kits with compressed air actually useful or are they gimmicky?
Is it better to put together a kit myself? If so with what?
I've spent 2 years riding so far and never had a puncture.
Now I've had 2 in 2 weeks - I figure it's time to get a kit.
ty