Re:
Firstly, it's not cheap to go 1x10, well, not as cheap as you might first think anyway, maybe you could try 1x9 for a while and see if you still want to go that route?
The deciding factor in me going 1x10 was that my chainset was knackered, and rather than pumping money into a replacement it seemed a good idea to go the 1x10 route and then sell the remaining 9 speed parts (mechs, shifters) to offset some of the cost.
I went with Shimano Zee components, fairly cheap, reliable, works well, you might also want to look at SLX components.
1. Rear mech, with clutch
2. Rear shifter, 10 speed
3. Narrow-wide chainring, round or oval, whichever you prefer. I went with a 30T Hope Retainer chainring.
4. 10 speed cassette, I went for a Deore cassette (11-36 i think) but with this you cannot split it apart and add an expander sprocket, you need to get the XT cassette for that. If you want the wider gear ratio then add in the cost of an Expander sprocket as well.
5. 10 Speed chain.
I soon got used to the 1x10 setup, ideally I'd like an extra gear for climbing, but most times if I can't get up it in 30/36 gear then it's usually just as quick to get off and push anyway!
And with the 30T front ring I can run out of gears, usually on the road I would say, but I don't ride much distance on the road usually.
Obviously you can run whatever size chainring you want really, but for where/what I ride a 30T suits me.
I went from 2x9 to 1x10 and I thought it would feel like taking a step backwards, but actually it's quite refreshing, you work with the gears you have, there's more room for the dropper remote where the front shifter used to be, and I've not dropped the chain yet, despite riding some really rough stuff.
If you ride more xc type trails, or on the road qute a bit then 1x10 may not be best for you, but I guess you don't know until you try it.
You might want to wait and look at Shimano's XT 11 speed Cassette coming out, with a 11-40 range (I think) which means you don't need to spend ££'s on an expander sprocket, although having said that anything new, and 11 speed, is going to come with a price premium in any case!
In summary, try it, you might like it, but be aware it's probably more expensive then you might first think.