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You'll be fine. It takes time to understand the combat and mechanics, but once you'll get the hang of it it's a very fun experience. The village quests handed out by Hinoa are like a tutorial, solo-only quests with smaller health pools etc. It's best to try out the weapons there to see what you like the most, and after that you're good to go to tackle the hub quests from Minoto. These are seperated in Low & High Rank and can be played with other people online. If you have trouble at any poimt of time, remember that you can customize your buddies! Palamutes are more damage oriented, while Palicos are supporters with a wide range of skills. There's also the Defender Armor and Weapons which can help you clearing the early game, but since it's made for people who just want to get to the expansion ASAP, it's not adviced for newcomers.

And yes, there are still enough people that play the base game :)

Absolutely agree with @[email protected].

There will be a large text dump at the start of the game to explain every little mechanic. I suggest you mostly ignore those for now, you can always read them later from the tutorials secion of your menu. Grab the weapon that seems the most interesting and start with Hinoa. Thats the start of the main "story" of the game, if you complete them all you can skip the first few levels of the hub quests.

Plenty still play, I have solo'd every monster up until the last 2 DLC, but if any are giving you trouble you can always host an online hunt, someone will most likely join.

I would recommend sword and shield, longsword, or dual blades as decent starter choices. Though if something else clicks, feel free to use that one. I started with charge blade, it was a hurdle but it is my favourite weapon.