The tourney scene is the best it's been in years. The main forerunner in this and the most popular by far is the CPPS series based at Penkridge, this 2 day event sees thousands of players each month battling out to be the best in their respective divisions. There are other tournament series available how we this is the big one in the UK.
As far as guns go, your choice is only limited by your budget.
Most tournament markers are very similar in terms of reliability, ease of use and efficiency and some can be picked up very cheaply. Each has its differences and people have their opinions and favourites for a variety of reasons.
Watch some YouTube videos of different markers and if you can see what people are using at your local site and ask to have a try (most paintballers are more more than happy to show of their kit)
Here is a basic list of different markers for you to check out:
Planet Eclipse
1) Ego (variants from 2007-2011)
2) Geo (1-3.5)
3) LV1
4) Etha
5) Etek series (1-5)
Dye
1) DM series (8-15)
2) NT 10/11
3) Rail series
Empire
1) Mini and Mini GS
2) Axe (and Axe pro)
3) Vanquish
Smart Parts/Luxe
1) Ion
2) Shockers
3) Luxe 1/1.5/2.0
4) Shocker RSX
Angel
1) A1
2) A1 fly
Macdev
1) Droid
2) Clone (VX and GTI)
Bob Long
1) Victory
2) Marq
2) Insight
4) G6R
These guns cover a vast array of prices from sub £100-£1000. Some are easier to maintain than others, some more reliable and some look better the choice depends entirely on what you are looking for.
There are many different markers available (and many I haven't mentioned here) but one of these would suit you well. Do your research before you buy, decide what you are looking for in a marker and then search the classifieds. A bit of work goes a long way to getting something perfect.
The classifieds here are a great place to start, once you find something you like the look of in your budget do some research on the gun and ask people what they are like and you won't go wrong.
In terms of a compete setup, make sure your air bottle is in test and has plenty life left (ideally coming from a reputable seller also). The three main hoppers used in today's tournaments are the Virtue Spire, Dye Rotor and Empire Phropecy Z2, all of these are very a capable hoppers so chose which you prefer the look of (again watch some
YouTube vids of them to aid your decision)
The best two bits of advice I'll give is
1) Don't blow all of your budget on a top end gun and all the kit and leave yourself no money actually play. The amount of people I see do this each year is enormous and hey soon leave the sport as they can't afford to use their expensive kit.
2) play as often as you can and enjoy yourself. it'a much more fun playing the game rather than polishing your kit, get out as often as you can and shoot people up, you will get much better much quicker shooting people rather than talking about it.