2ds isn't bad, it's just not ideal. I originally played on a 2ds until I played on a 3dsxl screen. The size of the screen really does matter. Plus you get 60fps more consistently with a n3ds.
Find a weapon you like and stick with it, at least for a while. If you go with multiple different weapons you might be slowed down a fair bit trying to upgrade all of them simultaneously.
Learn the maps. You should be able to navigate your way to anywhere from anywhere on any map. By the time you reach high rank you want to have all the maps memorized, so don't worry about doing it all at once.
Since you have already played a MH game before this stuff should be obvious, but you'll want to be patient, both when hunting and trying to progress. It may even be worth your time to do a few Gathering Hall quests (online, or solo if you don't feel like playing online) just to upgrade your canteen/ingredients.
Never go on a quest without eating. Even having sautéd fish+dairy before a gathering quest will grant you some gathering related buffs, along with increasing stamina at the start of the quest without using steaks or energy drinks. Eating before a hunting quest will also grant health and various buffs depending on the combination of food you eat and the preparation method. Eventually you'll learn what combinations grant certain buffs.
Change settings in the options menu, there may be some settings in there that you'd prefer not having default (instant dialogue messages), for example you might want to change some of the gunner related things if you're a gunner. Personally I like having "orientation" set to type 2, which makes certain things easier and more consistent if you can get used to it.
Abuse the wycoon as soon as he's unlocked, he replaces the farm from previous generations and can do a bit more.
Talk to eeeeeeeeeeeeeeeeeeeeeeeeeverybody who has a yellow speech bubble above their heads.
Just about everything you need to know to beat the game is discussed by NPCs, sometimes as subtle hints. Of course, you could always research online.
Mounting is a large part of this game. If you're playing online and somebody mounts a monster you'll want to stop attacking it or you'll accidentally knock the hunter off. If you're climbing a wall you can press A to jump off of it (If you do this near a canopy you can grab the canopy above you and climb up), or press B to drop straight down. After pressing B hitting X will cause you to do aerial attack from the wall. If you use a weapon with a forward dodge roll you can quickly grab onto a climbable wall by rolling into it and pressing A, instantly sheathing your weapon in the process.
A lot of people get confused about this so I'll explain it now. Eventually you'll have the ability to get multiple cats. You have the Ace Palico (the cat you customized at character creation) and then sub palicoes. You can have 5 first-stringers and you're able to take one of them with you on hunts, but you must have the Ace with you. It's either no cats, Ace, or Ace + sub. By default the ace palico has the 'leadership' forte, but depending on the fortes of your first-stringers he will gain different skills during a hunt. For example, he can blow a healing horn if you have two healing first-stringers, and blow a demon horn if you have two attack first-stringers. If you have two healing and two attack first-stringers then he can blow both a healing and a demon horn. Having more first-stringers of a certain forte will enable more skills of that kind to be used. Finally, the sub palico you bring doesn't have to be the same forte as the first-stringers giving the Ace his skills, so you can have 4 attack first stringers and bring a defense sub with you, and the Ace will get the attack skills from the other cats.