With changes to the game, especially the introduction of Realm Buffers, pretty much any class except pure healing classes can find somewhere to Solo. You need to find the class you like playing the best. Just start a toon and follow the Startup Quests and see how you enjoy playing it.
In big raids, usually all the required toons are present, so again having one you enjoy playing is best.
For small groups, you will find the best choices are: either Shield Tank (Go Midgard Warrior for your first time, you can play with other ones later and join the ranks of alt-ohlics), PBAoE Caster (Go either Midgard Spiritmaster or Hibernian Enchanter for your first time) or Heal/Buffer (Go either Midgard Shaman or Albion Cleric for your first time). Of these, only the Warrior is really useful to play Solo though. Healing class is the hardest to solo, unless you spec heavily into their casting line, in which case they aren't really a healing class any more.
On Gaheris you can have 10 toons in each of the 3 realms (i.e. 30 toons) so it's well worth playing about to find one you enjoy. Create it, play it for an hour of so. If you aren't having fun, try a different style of toon or a different realm.
Some people enjoy all classes, but hate a specific realm. Some people enjoy a specific class type and hate others. Most of us have the full 30 toons rolled and equipped. And then have to decide which to delete when we want another.
Find an active guild you can chat in. They'll help you out a lot, plus gives lots of specific tips to specific toon types.
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