In the Scrap Junk shop, buy the items and
then go back to the dinosaur dude. Select
"Sell" and put the cursor on "HyperionBazooka".
Press "O" a few times. You'll find that you have 7 free
items to gouge on! Look for ExcelShields in the upper
right - that's the best thing you'll find here.
The quality of the items will go up if you sell RepairKits.
Again, after the Gold Trick you should not have to do this
much. The best place for getting new abilities is the Bio
Research Lab in Shrike. Use your worst attacks against the
enemies (you can rest for free nearby). Quicksave after
every battle. Don't wander too far; there's no treasure.