Personally, I'd recommend playing all types early on and get a feel for them so you can be flexible if need be. My two favorite types to play as are defense and healer. I'll do my best to avoid DLC moves and mentors, but I can't remember which ones are DLC for every single character, so I'll try to give alternatives if I'm not sure if they're DLC or not.

Mentors: I'd recommend for defense type, going with Hiruzen (the third hokage) for your first defense type, then probably Tsunade as your first healer. I don't remember if Tsunade is a DLC mentor, but if she is, then go with Sakura and Kabuto as your first two. Kabuto's Cellular Extraction Jutsu is great for healing in a pinch, and Sakura's Cherry Blossom Clash is good in the same way heavenly foot of pain is, but doesn't have the range or damage output that Tsunade's move has. Mitsuki has some good moves as a defense type as well, but none of them have good range, so thats why I'd recommend going with Hiruzen first. Minato is a great beginner mentor as well, as he has the Flying Raijin Level 2 and a great ultimate. Itachi is a really good beginner ranged mentor.

Jutsu: For attacker, I'd say the Vanishing Rasengan (Boruto's move) is really good. Quick start up, great range, decent damage (not the best, but decent) and great stun lock. I also like Leaf Rising Wind (which is an uppercut that allows for extended combos) and Leaf Barrage (I don't remember the exact name, but its a heel drop that can be used to both bounce an enemy off the ground into a longer combo and yeet bitches into pits). For the ultimate, I'd go for Boruto Strike as it charges really fast, or Minato's ultimate for damage and the ability to hit multiple targets. For ranged, Phoenix Flower Jutsu (starting move) and Phoenix Scarlet Claw (again, don't remember the exact name, but you get it from Itachi) are pretty good. Outside of DLC mentors, I personally don't think there are that many good ultimates for the ranged type, outside of really situational ones, so if you're willing, you might want to spring some cash. Defense, I'd say go with Dragon Bomb jutsu, Shark Bomb jutsu and for your ultimate, I'd go with Kisame's, which is just a bigger shark bomb. Healer, I'd recommend Cellular Extraction jutsu and Heavenly Foot of Pain, and I'd also not recommend using HFoP on stages like the Hidden Sand or Hidden Cloud, because you can very easily slam dunk yourself into the endless abyss. Again, exchange HFoP with CBC if Tsunade is DLC. Also, stick with the basic substitution. It has a 20 second cooldown and does exactly what you need it to do. Other people may say otherwise, but I have personally never found a use for any of the gimmick subs, like Shadow Clone, Water Clone, Sand Clone, etc. They take a full 10 seconds longer to cool down and if you're subbing, you're probably gonna need to be able to again, so I'd stick with the basic sub. That is, unless you buy the Shisui mentor DLC. His sub has a 25 second cooldown, versus the 20 second cooldown, but it buffs almost all of your evasive abilities.

Weapons and Ninja Tools: for attacker, claws seem to be really popular, but I don't like them all that much, personally. I prefer the ninja knuckle knives or just hand to hand. Ranged, its kinda whatever for me. As far as I've noticed,, none of them are so different that I'd notice that much.. Whatever looks cool, more than anything else. Defense, Scythe's are great for speed and combo potential, but I prefer the long sword and executioner's blade for its strong attack, which is good for clearing out clumps of enemies. Healer, I'd say stick with the ninja sword. Its best for combos and I can't say I like any of the other weapons that much. Ninja tools are pretty universal, except for defense and healer. Attacker and ranged, stick with kunai and senbon. Defense, I'd recommend blast bombs (I think that's the name) or the mines. Healer, always go with the healing tag.

Clothing: Almost universal. I'd say go for maximizing either combo potential or ninjutsu. For the top, either go with the perks Dogged Determination, First Blood, or Tenacity Rising. That last one makes it easier for your jutsu to cancel out other jutsu, which is really useful, as most jutsu do good enough damage anyway. Master of Medicine is good for healers, but that's up to personal preference. I usually stick with First Blood for my healers. Bottoms, go with perks like decreasing substitution time or reduce ninjutsu damage (I don't remember the perk names), or, for healer specifically, Armed and Dangerous, which decreases ninja tool cooldown time, so you can use the healing tag more often. Accessories, I usually stick with whatever works best for that type. For example, attackers, I usually use renewed focus, I believe (the one that makes breaking guards easier). Ranged, one in a million, which massively decreases cool down of ninjutsu when an enemy is defeated. Defense, vengeful fury, I think, which increases attack power when an ally is downed, and healer, go for the one that massively reduces ninjutsu cooldown when your health lowers to a certain level.

Combat: Make use of blocking and evading. It may not seem useful, but trust me, it'll keep you from getting absolutely bodied. You can block in the air, so you're not completely defenseless when jumping. Attackers and ranged are pretty simple, all things considered, but you can extend combos or increase the damage at the end of your melee attacks with kunai/senbon. Those are really good for finishing someone off if your melee combo didn't quite do it. If someone is prone on the ground, you cannot hit them, even with ultimates. They have to get up first. You can roll out of the prone position, but I'm not sure how to do it reliably. It just kinda happens sometimes. However, if you can figure it out, you have I-frames for the whole animation, so it can get you out of a bad situation. Slamming into a wall turns off the lock on and can be combo'ed after they peel off of it, which goes for you as well. Light attack combos can be finished with a strong attack, which I think does more damage than a light finisher, but there's the possibility of them falling out of your combo, so use it mostly when you're on the ground.

Last but not least, have fun. Its not a game to take seriously. There's gonna be some real frustrating shit, but don't let it get to you. The game is trash and we're all trash people for playing it.