So far in RDR, I've been forging ahead with campaign missions. However, recently I stopped at a Gang Hideout and walked away with a new (and quite awesome) Repeater, as well as access to the Fire Bottles.
It strikes me that there may be some side quests with rewards that would make my life easier, but even after browsing the web for the various side quest rewards, I can't determine which are actually worth doing early, or even which are possible to complete before I've finished the main game.
I plan to attempt 100% at this game, so I'm going to do everything eventually, but knowing now what makes the most difference gameplay-wise would be helpful.
Are there any particular side quests that I should prioritize? Which are they, and at what point should I attempt/complete them?