So I am sitting on 50 niche adsense sites, some have done very well for and I will be keeping those. Others I will be looking to completely drop or flip. My question is how do I determine what to sell and what to throw away?

All sites have unique content, almost all are EMD, All have had some sort of backlinking done and all of them have made me some money ( $7-$500 for the last 9 months). What would you consider posting on flippa?

I feel the need to cull my stock of sites as I can no longer put in the effort that I once did and I want to focus on the sites that are making me decent money.

Just sell them all as a package.

it all depends on if you want to sell seperatly or together. If together then sell it. Otherwise bundle similar sites and sell those. I wouldnt reccemend selling singular sites with low profit unless bundled. If you need help selling let me know!

I would sell the ones that are will decline in visitors over time. If you see a keyword lasting for a long time, keep it as it will make you more money in the future. Selling in group, as mentioned above, is the best way.