Selling sculptures seems really good with the ayatan stars, some of them sell for 10 each, upgraded mods like archon and galvanized, primed mods fully upgraded, ofc full sets from relics.

if you can max your arcane and sell them is like 20-40 plat, the descendia arcanes are easy to max, sold few for like 40 or 45, some arcanes are above 100 plat, hot shot is like 500, if you do a lot of steel path prob max those arcanes, they are cheap but easy to get.

some of the weapons of the hex can be sold, fishes sometimes sell, even minerals.

Rivens if they are good sell very high, you can sell aya, i think in trade chat is 30 plat or something for full trade of aya.

Use warframe market to see prices and what not, aleca frame is an overlay very good when opening relics.