[Closed] Advice on 1 x 11 set up please (ratios and what parts?)

I've been having trouble with my 2 x 10 setup on my Ibis Mojo HD3 for a while and I have a more xc type bike that would benefit from these parts so I'm looking to switch to a 1 x 11. I've run 1 x 10 before but missed the low gears a bit so......

1. What's a good ratio for all day 'all mountain/enduro' type riding? I'm guessing I'll want an 11-42 cassette but what about the front ring? I don't want to go too small on the front and risk a lot of chain slap.

2. Budget is a factor so I was hoping not to have to spend more than about £50 on the cassette. I wouldn't need cranks but would need derailleur and shifter and chain.

Thanks.