Hey there, and welcome to Animus.
Before you go on to donating and gearing up a class, you should learn about each individual one. Also, some classes require more money and gears than others, and vice versa.
My recommendation is that you go ingame and frequent PVP, look at different classes and how people use them (although some people will not play their class to 100% potential), also, look around at how each class plays their role and maybe you'll determine which is right for you.
In this server, WS/BS are generally mobbing classes; LKs are versatile and are decent/good Mobbers, solo killers and tankers; Assassin Crosses are generally straight up killers, some of them use flee and others focus on high Vit with high reductions.
Priests/HPs focus on support, but others have used them for mobbing and killing in maps loaded with undead monsters; Champions/Monks are also versatile in how you can melee, burst damage (asura) or do a ranged attack (Finger Offensive).
There are a lot more classes that I'm missing out (Bio, Pally, Prof, Minstrel, Sniper, High Wiz, etc). If you have any questions on them feel free to PM me and I'd be more than happy to help you out.