You can sell grey stuff, and also magic gears no one buy, in Cheryl or any Vending Machine. The gain is very low but it's better than destroy. Same you can do with Sit Hyperchip. The Exp Hyperchip, instead, need to be destroyed or sold to other players in Gloria, some of them have good proce, L4 above all, if I'm not wrong, can reach 200 gold.
Low level potions, sell in Cheyl same way as trash drops and magic gears, they can't be upgraded.
And remember, you can do everything to have your bag clean, but it will be always full in few time. It's one of the most important problems of the game. Our bags were aimed to game cap level 29 (year 2013). Every patch after 2013 added important stuff, you will find Hexwaves, different cards, pieces to craft gears, medals of every kind, skillstones, relics etc etc etc etc... But the bag is still the same as 2013, so every 30 minutes it need to be manually cleaned in some way.