It's hard to look at a picture and know that is what you want to wear to the next SCA event or Renaissance Festival; but sometimes it is the best option.   Before I started sewing myself, I had a heck of a time finding good quality garb online.   I noticed a lot of problems that hopefully will be helpful to both buyers and sellers.

1)  Always ask about fabric content or put that in your listing.  I was the unfortunate victim years ago of finding what looked to be a beautiful gown online.  I quickly bought the gown because it wasn't overly expensive and was my measurements.  When I received the gown, I was horrified to find out it was nothing more than satin lining fabric, not heavy satin.  It felt like a plastic garbage bag in my hands.  I never wore it. 

2)  Always ask for or put pictures of the inside of the gown.  This shows really how "good" the quality of the gown is.  You can see the seams, stitches, and lining this way.  You can tell if it's all frayed or if it's nicely trimmed.  You can tell if it's lined or not.  Pictures go a long way.

3) Never buy from a person that doesn't put up a picture of garb they've made.  I've seen in the past and even on some online venues today that certain sellers only put a picture of the pattern they will use, not an actual piece of garb they've made.  If you haven't seen any garb patterns, I'd suggest you look at them before you buy your garb.  It will give you a good idea of what garb is out there and be able to recognize what is a pattern and what is really garb.

4) Ask questions before you buy.  This is common sense with any item but even more so with custom made garb.  If you need something ASAP, ask.  If you really want a specific color, ask.  If you just want to make sure the seller is a real person, ask a question like "can you tell me how long you have been sewing and what types of garb you typically specialize in?".  You'll probably just get a general answer to the last question but it will give you some insight into the seamstress/tailor's personality.  Remember, you actually have to work with this person to get your garb and to get it to your measurements and colors.   It can be a hassle if you have different ideas on what the auction means.

5)  Always check the feedback rating.  If it's below 99.2%, double check why this person received negatives or neutrals.  Also check to see if they have sold garb before.  If they have a low feedback rating and don't seem to have sold garb before (as in, actually have feedback in regards to garb they sold) , back away.  (A side note to this: if their low feedback is just due to slow shipping, that is fairly normal in the garbing community and they are probably fine.  Good quality custom made items to take a lot of time.)