Well, the game is primarily about loot. Itās a kill/loot/repeat cycle on steroids; itās what it is. So you wonāt be able to get away from loot. Thereās little role-playing per se, but what there is is pretty much āme hero, me smash demons big!ā The bigger the fights, the bigger the explosions of energy and effects, the better. The sorting through items is something they have streamlined, though; at one point blues become nothing but crafting fodder, and later on, pretty much all yellows are trash too, so itās pretty easy to just hit salvage all at the blacksmith. The tooltip comparisons are simplified and much better now, so itās pretty easy to tell very rapidly whether a piece of gear is an upgrade or not. Once you get to the (far less numerous) legendaries and set pieces, you can afford to spend more time comparison shopping, and itās more fun as well.
As for characters, matter of taste. I love wizards. Huge damage, lots of risk as theyāre fairly squishy, and easier to run once you have a stockpile of crafting materials and paragon levels from something else, but very fun. Iād recommend though a Witch Doctor or a Barbarian for a first run through. The WD is a blast, and very survivable. The Barb is classic Diabloābig sword, big moves, big dumb fun. Not my personal favorite but it is a great way to use those honkin huge swords you find. The Crusader I find boring, but YMMV. Monkās are great too, in their own way. I really have only one character Iād personally stay away from, the Demon Hunter. While I wanted this character to be really great, and it was the first one I ever tried in D3, to me itās a fragile, not terribly fun constant kiter that has sub-par gameplay. Lots of mobility options maybe but to me it has the fragility of the wizard without the damage output or flair. As always, YMMV.
One thing to note is that on the leaderboards for four-person hardcore greater rifts, you have to get to something like 54th to find someone who is not a Barbarian, Monk, or Witch Doctor. Gives you a clue on which classes are the most durable and successful overall probably.
Co-op is indeed practical, but Iād recommend it only with friends or people you trust and know. Even in softcore, too many asshats out there. Most of the power players play in two or four-person groups all the time. I play solo mostly, but the few times my guildmates jump in the experience and loot increases a lot.
As for tips, play it your way. If youāre playing softcore, play around with difficulty settings until youāre happy. Play at your own pace. Donāt worry about endgame builds, just experiment with all the whacky stuff the game lets you do. Toss some spiders! Shoot electricity from your hands! Dual-wield crossbows and shoot flaming bolas! Whatever floats yer boat.