For weapons don't worry about the symbols other than for sunsetting (and you can tell if a weapon has been sunset as it will have a max power level when you inspect it (same for armour).
What to keep - armour is relatively easy, if its total stat score is above 62 say, I'd keep it at this stage, lot of people worry about stat distribution but at this stage just collect stuff with high stats overall.
Guns is harder as there's a confusing large amount of perks some of which change a guns performance quite a lot. Also each gun has a 'masterwork' perk which can be a huge deal - for example range on shotguns. So how do you know what to keep -
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light gg is pretty good at helping sort the good from the bad, although it ignores masterworks so just use it for perk ideas. Always good to look for perks that compliment each other , maybe buffing damage and reload which tend to be the best things to go for.