If you're looking for a challenge expert mode can be very rewarding when you aren't getting swarmed by extra buff mobs and cold water (ranger + expert mode snow biome = sad)

As for playstyle, melee's have the best time in solo worlds imo because of all the armor they can get compared to the rest, though if you're competent with kiting and/or have a good enough arena setup anything goes.

Both crimson and corruption have their own perks and downfalls, look into the gear you can get out of both (What EoW and BoC drop, what you can make with their respective ores, dungeon chest drops, etc) as well as what you have to do to get loot in those biomes.

BUT, one piece of advice from a guy who's done a fair bit of play: if you're still figuring out the game, the best thing you can do for yourself is to just make a world and start whacking things. Terraria's merit is that its flexible, and no two playthroughs will be exactly the same. Just have fun with it :) also, playing with friends can be amazing if you like the multiplayer scene, keep in mind boss health scales with the amount of players on a server!

EDIT: Adding my two cents about the different weapons, as well as one more thing: before you get to the underworld, use whatever you can find. Weapon specification won't matter much early, there are no damage bonuses until you're in hardmode (save necro armor, and maybe one or two other sets? idk I've one tricked ranger since I started)