all depends if you plan to race or use it on the trails.
saying that I have a 34/46 11-28 and use for both racing and trail riding (trail riding around west pennines) anything more and you might want more cogs on the back.
I also need cross levers on the tops (saves the back from long braking in the drops).
tyres – if its trail stuff I use landcrusers they’re cheap and very hardy (3 peaks tyre of choice) ok on the rd too. if racing have a look at the challenge grifo’s
I’ve got some mavic open pros rims which are very stiff & strong
I have rival levers and apex rear mech (get the cheap mechs – mud and racing will destroy them plus ‘high end precision parts’ will be lost on the trails or caked in mud)
a lot swear by 105 groupsets!
I changed my bars to a shallow drop – I didn’t like getting so low on regular drop bars. get some wide bars for stability! not narrow roadie bars.
thats about it.
do have a go at your local cx races you’ll love it! there low key and some even ride on mtb’s.
you’ll love it (I hardly touch my mtb these days)
hope this helps
Craig,