While the common thought is to buy a new bike, if you do upgrade look at parts that will either work on another bike (probably better to 120mm than 100mm forks), or ones where its handy to have additional bits (wheels).

Wheels are normally a good place to start, and one where you'll get most benefit now and later - try Hope Hoops (circa £250).  And look at tyres that work for your riding/weather now, not allrounders.

I have the suspension that came with it; got the bike about 3 years ago; te suspension is the Suntour XCP - 75. Does the 75 mean 75mm? Also can you get forks which are bigger than 75mm to fit my bike; or is that why you have to get new wheels. Because I have never had any problems with my wheels that I couldnt fix;

(I recently bought new threads which suit my surface perfectly, and im currently very happy with them)

I dont know which kind of suspension to search for; I mean what kind of TORA would fit; im really new into the world mtb. Could you recommend a particular model?