Separate them by collectibles type.
See if you can find a forum or website that identifies these collectibles by name
Check ebay sold for what the item has sold for.
If the item is heavy and cheap (less than $100), look at selling at Mercari and choosing Fed Ex or UPS as the shipper ($100 is the max insurance / declared value coverage that they will cover, but they ship all over for a fairly good price). Frankly, if the item weighs more than one pound, it's good to look at Mercari and choose Fed Ex or UPS.
See if there is a local place you can consign the items too (assuming they have high traffic)....
If you're looking to get the most for your money and don't mind selling individually and dealing with the hassle, eBay is ok. Otherwise, I would check out local places (Offer Up, Craigslist, etc.) that you can meet the person at a local place and accept cash