In RotMG there are a variety of classes. Each with their strengths and Weaknesses.
Here are some basic guidelines in case you have trouble deciding what class you like.
Remember, if you keep dying sometimes its good to try something new!
One of the easiest classes to play and also one of the most likable. The priest is also relatively easy to max (the one challenge being to get a lot of wis). The heal makes it a great class in groups, and you can farm in godlands without farming for potions or returning to nexus for a heal. Priests are also great for soloing dungeons. The major disadvantage with a priest class is the low damage output, which makes killing gods very slow, and soulbound drops slightly harder to get.
Sorcs are very good at getting sb damage on gods, especially when farming in large groups. Their special doesn't need to aimed, and can hit multiple enemies. Like priests, however, they have large range but low damage output. Unlike priest, however, they have little defense and no heal, making them not ideal to do dungeons or hunt gods alone.
A really great class to farm in godlands. Necromancers can kill gods very fast, are relatively easy to play because of their range, and can heal. Their heal is somewhat unreliable, so occasionally they might consider having a few hp pots in backup. Necros can easily get sb damage and can solo dungeons well. One disadvantage to necros might be that in large groups their heal causes major lag (lagromancers). Necros are also robe classes, so they should be careful when low on hp (unlike priests who can almost always guarantee hp above 50%).
Wizards are one of the most offensive classes. Their spells make it easy to smite enemies from a long range, especially if you play in de-centered mode. Wizards also have one of the highest overall stats and expensive equipment, which makes making a maxed Wizard quite expensive. Wizards are one of the best classes to get sb damage, and can kill gods incredibly fast. One disadvantage is that the wizard is a robe class without a defensive ability. This means an unmaxed Wizard might have some difficulty completing dungeons solo.
A great Mystic can be a great asset to a group, but a terrible one could be largely hated by the group. Mystics are very tactical. Their stasis can be used to crowd control, escape enemies or allow group members to get into better attacking positions. They have high range and low defense. Their main drawback, however, is that they lack the firepower that Wizards and Necros have, which makes them less efficient solo.
Rogues are one of the best solo classes. Their ability enables them to kill pretty much anything alone. Given time, they can solo almost any event god or dungeon. In groups, a rogue has to be a little bit careful, but their ability is still useful to sneak behind enemies. Rogue's cloak can also enable them to skip large segments of dungeons, which makes dungeon farming efficient. Rogues have moderate range and moderately low damage.
Assassins are primarily used to get soulbound loot. It is extremely easy and relatively safe to lay large numbers against bosses using an assassin. Assassins have medium range, moderately low damage, and moderate armor. They are not very spectacular when farming gods or doing dungeons.
Tricksters are a very tricky class :). Their special can be used in a variety of ways. They can teleport to better firing position, teleport away from danger, or create decoys to divert enemy fire. They are, in my opinion, extremely fun to play, albeit a bit risky. It takes a considerable amount of skill to effectively use this class, however, the way that you play tricksters is very different from the way you play most other classes. I think it's worth a shot to try this class out.
Archers are one of the most popular class. The stronger bows can fire 3 arrows at once, and each arrow pierces. This gives archer a potentially high damage output and makes them ideal for crowd control. Their range is slightly lower than staffs, but their armor/hp is better than robes. This makes them ideal to farm gods, granted they bring potions or farm with a healer. The quiver gives an extra dex boost, making them slightly more offensive than huntresses. Their ability restricts the movement of the enemy, enabling the group to attack it. Archers are stronger closer up because more arrows can hit the target.
Similar to the archer, the huntress has 3 arrows that pierces, making them have potentially high damage output and ideal for crowd control. Their special adds to their ability to crowd control and could give a tactical advantage when ambushing enemies (and dragging them onto traps). Like archers, Huntresses are stronger the closer they are to the enemies.
Paladins can heal and boost allies, which make them a beloved addition to any group. They have high armor, damage, but have low range. Although their low range may make it someone tricky to fight gods in swarms, their heal means that they can easily take on gods in small groups. If they are in a group with a warrior, the whole group can do immense amounts of damage. Like all sword classes, their low range could be a bit tricky, especially to newer players.
Knights are the ultimate tanks. A maxed knight has a whooping 40 max def. The knight special can stun, which is great for taking out enemies in groups, or dealing major damage solo. Knights are very strong when there is a healing class nearby. Like all sword classes, their low range could be a bit tricky, especially to newer players.
Warriors can boost their speed and everyone else's dex. They are agile, and can do immense amount of damage in short bursts of time. A really skilled warrior can minimize damage taken. Warriors are great in groups, and often if they are with a paladin, the double boost is a powerful combo. Like all sword classes, their low range could be a bit tricky, especially to newer players.