A few tips so you don't waste too much time early on and can get to the real meat of it faster:
- Pretty much all the weapons that are actual upgrades will be given to you via the main chapters (or unique ones in a handful of side quests), so while you can grind cash until you can afford a scoped rifle or decent shotgun early, it's honestly not worthwhile. Instead, spend your early game cash on quality of life stuff like better ammo and ammo capacity (ideally, you want a decent stock of Express Ammo for your favoured guns at all times). Oh, and of course, hats...
-On a similar note, keep an eye on the missions that teach you how to improve the camp. Investing in stuff like a better stocked armoury or medicine wagon early on and keeping those stocked up will be worth it ten times over by the end of the game in terms of both time and money saved at shops/hunting/crafting. You can eventually work up to things like a fast travel from your camp, which saves plenty of time in the late game.
- Try and learn one thing at a time when you get started. The early missions actually double as quite decent tutorials in this regard, but often introduce concepts that they only give you one or two chances to practice or that flash by in very small text boxes. All these tips can be found in the menu, so it's well worth reviewing and practising if you find something you want to do a lot of, if you get into hunting or fishing for instance.
- It's been mentioned, but at least start Stranger Missions when they pop up. Some are lengthy collectathons that can be safely ignored outside of a 100% run, but it's easy to miss some of the game's best content if you proceed too far with the story before picking up the first parts of those missions, and the game isn't always clear about when gak is imminently approaching the fan and you're about to be thrown into the next Chapter.
- More of a story tip than a game tip, but get to know the characters around camp as soon as you can. Talk to them, do tasks for them and generally pay attention to their goings on as you settle into the game. The gang are the heart of the story even moreso than the
NPCs of the first game, and it's through them that RDR2 delivers its highest highs and lowest lows. RDR1 is John's story, but here, the whole crew is center stage and the game is at its best when you really get to know them.