Now you've asked two questions here: how to select the marketplace available. For this you have to consider certain factors like engagement in the marketplace, community building and the volume of trading available. There are some well known platforms like opensea and foundation etc. You can easily choose marketplaces by doing a thorough research on the points mentioned above.

Now the second question is whether you need to choose a polygon or sol network. So it depends upon whether you are price conscious or speed conscious. Sol offers a high speed transaction but at higher fees on the other hand polygon offers low transaction fees but slower transactions compared to sol. So it's your choice.