There are significantly more quests than you need to advance levels and eventually you get level 30+ having done all the side quests and there will be several unfinished missions for recommend level 7-20 that become worthless unless the story/character behind it interests you.
Definitely grind early missions as they are basically tutorials and also give you lore on all the factions, don’t worry too much about gold as you will rarely be able to buy weapons better than what you find.
By mid game you’ll have tons of access to loot for selling and will probably be more interested in spending money on refining/upgrading items than buying mediocre armor and weapons.
The bombs and oils are great if you keep them upgraded
Never sell ingredients you don’t have a billion of, you can buy a potion to redistribute your levels and switching from magic/physical build to late game Alchemist is really strong and fun and changes up play style.