Okay -
1) if you can't describe the color, you can't sell it online. Those mottled/heathered effects that you say to yourself "is this gray or is this brown?" Wait, or is this blue??" In a physical store it might be okay, but online not unless its a full suit that is drop dead spectacular in some other way. it can't be photo-ed to be able to tell what it is either. I am not talking about tweeds. These i am talking about are usually wool blends that are smooth to the touch. I would stay away until you get really well versed.
BTW...not talking about color change silk or sharkskin....pick those up 99% of the time if the quality is decent.
2)Pass on Jackets that really look lost without matching pants and can't be really worn as "sport coats" unless they are exceptionally old or until you know what you are doing/have a built in market. A lot of Double breasted jackets don't go single unless they are from the 1940s or unless they are a slimmer cut, high button, millitary inspired.
3) Buy cashmere even if you have to save it a few months. Condition is CRITICAL because everyone else is picking it up too. Any color, but the patterns sell best. No storage smell, moth holes will be tolerated.
The rest REALLY depends on who your customers are.
For me, wild patterns that you would normally find in poly, but done up in wool, cashmere, silk, or other high quality materials and constructions - my customers love em. But i can't say if yours will. Your customers might like something totally different. Classic, 3 button, skinny lapel early 60s blazers in tweed and 50s notched cuffed jackets do well for me too.
Look at labels. If its spectacular it doesn't have to be a famous name. Folks just like labels.
Also, research, reasearch, reasearch...what labels are mass marketed and when did they start that. When did the designer still have their hadn in the designs? And look to see what men are wearing this season and next.