IMO: The World of Magic is a free mobile mmorpg made by COM2US. You can pvp, farm bosses, fight for your side (Siras or Lanos) on battle fields, and make new friends! 😃 Here's the link to it. The game supports English, Korean, and Japanese.
Warrior is a tank, and has high armor points (defense) and hp. They can hold out for long in combat, and easy to train once they learn 'Sweeping Strikes' (a skill that deals damage to multiple monsters at the same time). They may need a healer to party with when training so that they can save expense of buying health potions. And it's fairly easy to get warrior item on the black trader (where players can buy and sell) because usually there are so many. Warrior is strong against rangers, though not so much against mages (of course, it depends on the gear and level in some cases).
As for ranger, rangers can kill their opponent very quickly with multiple damage. Rangers can solo in training, and quite fast, too. More quick in dealing damage to boss monsters, so they are good in farming. Ranger items are easy to get on the black trader. Rangers are strong against mages.
Lastly, mage. Once again, my favorite! >_< Mages don't need much money in early stages as they can act as a healer in a training party, and save gold from buying mana potions. They also don't need good gears (wand or armor) since all they have to do is give heals to the warrior. But once they level up, they will need a lot of gold to buy items because mage items are so expensive on the black trader. Not only that, they are kind of vulnerable to rangers, though they can buy time to either deal damage or escape from warriors by freezing or stunning them (or use fear if you can).
I would always choose a mage because I love to party with warriors and heal them, rather than solo-train.
Anyways, this is my first video on my character! I'll upload more as I play :D
By the way, this cute avatar above was made by Salya ♥