38t with a range of freewheels would be my choice. 46t would be too tall for most off road use.
Tyres - if you buy one pair then I think Michelin Muds are decent in almost all conditions.
Wheels - whatever you've got.
I'd stick with clinchers for your first year, much less faff and you learn how to ride them to their limits which should, I think, benefit you should you then choose to go tubeless or tubs.
38t with a range of freewheels would be my choice. 46t would be too tall for most off road use.
Tyres - if you buy one pair then I think Michelin Muds are decent in almost all conditions.
Wheels - whatever you've got.
I'd stick with clinchers for your first year, much less faff and you learn how to ride them to their limits which should, I think, benefit you should you then choose to go tubeless or tubs.