There are some users on the site *cough* JJGames *cough* who flood the site with a lot of games with relatively poor prices. They clutter the Marketplace and stand in the way of other sellers with their mass posting. If there was any way to omit users from a search, or even browsing through console categories, that would make the experience much better.

When looking in my wish list for cards I may want to purchase, It would save a click if there was a "buy" button next to each entry instead of clicking the card's page and then clicking the buy/sell button

Every item seems to be stuck at the last 30 sales.  The should be a way to look at the full history.

Would like the option to include Tag in the "what grade" and or "grading company selection" 

Can you please add the Union Arena card game by Bandai? Union Arena has been out in the United States for over a year and continues to gain traction and popularity among played card games. Each set is focused on a popular IP such as Bleach and Jujutsu Kaisen. 
The card game also draws a lot of popularity between card collectors. The alternate art or chase cards often maintain high value, similar to Dragon Ball and One Piece.

Add psa graded funko values

Add a feature where you can add autograph to your POP collection, autographed by who, who authenticated it and certification number.

Be cool if you can figure out how to track autographed POP value as well, but those other 3 would be great to start.