First thing to remember is pin collecting is very much a "marathon, not a sprint." Everyone is very eager to build their collection, and have success trading, but going overboard early is a good way to A. spend too much, B. buy the wrong thing. With over 100K pins, it's hard to find a person who has a pin who want, who wants what you have, and you both would consider the trade fair. The permutations are very high. I don't live near the parks, or have access to popular locations like DSSH or the CM stores, so before Pin & Pop Trade Arcades, I hadn't done much trading in like the last 10 years because finding good matches is so hard. So my advice is:
A. You are better off investing in your own collection, what you actually want vs investing in traders. Converting new pins into old pins is hard, because people with the older pins know where to get the new stuff too, have made connections, etc. There will reach a point where you will say to yourself, "I've spent too much on traders no one wants." So try to nip that in the bud early. The longer you are in pins, the more trader pins will find you by narrowing or shifting your collection focus, sales you stumbled into, pin lots of 5 you bought but you only needed 2 of them, etc.
B. I've always had more success with low value pins than higher value ones. Hidden Mickey / Disney pins and mystery/blind boxes. In the process of acquiring these type of pins for yourself, you are going to end up with duplicates. A lot of duplicates. But so is everyone else! Everyone is looking to complete some sort of set. Most of these are easy to evaluate for fair trades (sure I will trade my Loungefly blind box Alice pin for your Disney Parks mystery box Coco pin). Where with LE pins, people get squirrely fast because people don't want to have regrets by overvaluing or undervaluing the pins involved. This is where I have had great success in Pin & Pop Trade Arcades. Getting rid of my duplicates to help me complete other sets.
C. Some themes are perennially more popular than others. Certain princesses, Maleficent, Stitch. If you have the opportunity to attend a LE park release, event, or a shopping day and there is an opportunity to pick up an extra. This also goes for popular Series. If you happen to be at a park on release day.
D. It can take time for interest to build. I have had pins sit in my trade book for 20 years, and then one day people want it. Maybe, it's a pin for an attraction that is closing. Maybe, it's a movie pin that wasn't popular on release, but a newer trader, 5 years later has nostalgia for. There are traders that I buy, that I throw in a drawer and hope that in 3-10 years there is greater interest than now. The people who have access to the good stuff are going to be the people who can flip their pins, quickly, for other good pins. If that isn't your situation, people need to be realistic about other people's interest in what you have.