Thanks. That is great. I will definitely be looking a few things up and will check that video out. I will also be in here asking a few questions if that is cool? Just tell me to shut up if I ask anything stupid.
Ok this was my first MH ever as well, and now I'm G2 after god knows how many hours (probably over 150 at this point).
One of the first things I wish I had known more about at the start is the lock on system. It's not like Souls. To start, you can't lock on to smaller monsters at all. After a few hours you'll be ignoring the small monsters altogether.
For large monsters, touch the monster icon in the touchscreen to select the large monster, but only if you're in the same area and have both seen each other. Once selected, pressing L will swivel the camera to the monster, but will not lock on. You have to keep hitting L to swivel the camera to the monster. The reason they do this is because you're going to be hitting the monster in specific hitzones (head, leg, tail, etc) for a variety of reasons. If the lock on was like Souls, you'd always be hitting basically the same area, which would be disadvantageous in many situations.
The different hitzones on monsters can be used to either exploit weaknesses (like maybe the head is particularly weak to fire), or to break those parts to get specific materials for your weapon and armor upgrades.
There are no classes or character levels in the game that affect your stats or abilities. There are sort-of-levels called Hunter Ranks but they don't impart any benefit aside from providing access to higher level quests. HR 1-3 is Low Rank, HR 4-7 is High Rank, and HR 8+ is G Rank. HR comes from doing quests in the Gathering Hall (the online part, which you can totally solo if you want). You won't get access to that until a little bit into the game. It's kinda weird but the game is split into Caravan quests (solo only, Caravan 1*-6* is considered Low Rank, 7*-9* is High, and 10* is G, I have no idea why they didn't make it the same as Gathering Hall) and Gathering Hall quests (online or solo). They are similar quests, but not exactly the same. I would start by doing Caravan quests for a while, then jump into the GH once you feel fairly comfortable with your weapon.
Things that would normally come from leveling in other games come from armor in this game. Armor provides both defense and skills. Each piece of armor will have a certain number of points per skill. In most cases, you need a total of 10 points to activate that skill, and in most cases, especially early on, you will only get 10 points in a skill if you have a complete armor set.
Classes come from weapon selection. There are 14 weapon types, so 14 classes. Each weapon has a specific moveset that is 100% unlocked from the start. Upgrading a weapon will only upgrade the damage, not the moveset. I would do all of the weapon tutorials to see what weapon you like best, and stick with it for a while. Learning a weapon's movesets is one of the most important parts of the game.
To create/upgrade weapons and armor, you will need specific monster parts and cash. At this point, I always have kiranico open on my phone when I'm playing so I can reference what parts I need, where to hit the monster to get those parts, what elements monsters are weak to, etc.
I could go on for hours but already have a wall of text so just ask questions and we'll do our best.
Edit: Eat a meal before every quest (I think you need to be a few quests in to unlock the meals).