As others have suggested turning off the question marks is a good option.
One thing that you might think is helpful as a completionist when considering turning off the marks: The question marks that have some kind of story attached to them will be part of a quest you will get from talking to people, so you will be directed there through the quest. For example: Scavenger hunts will end at a question mark but you will get a quest objective marker for lets say, the Griffen pantaloons. You will not miss them if you just follow the quest and have the markers turned off.
The majority of question marks should be thought of as loot chests. You can get crap gear to sell/dismantle and materials. That is about it. Which ties into your question about gear. Craft witcher gear if you have the patterns. Witches gear is a nice investment because it can be upgraded. The master piece requires the sub-master piece as a component. Crafting the gear costs money and mats so if you are low on either turn the marks back on, clear a few bandit camps, collect loot to sell, turn off marks, and craft you gear.
Hope this helps.