We love the National Geographic books. My kids all love ocean animals. There is an awesome ocean book that they have. Check out ebay for great prices on used books. They are always in great condition when I get them off there. Specifically Thrift books on there is great. Also DK sticker books would be fun. I know they have an ocean one. Melissa and Doug has some fun books with ocean stuff like theirreusable sticker book, they have sticker mosaic books one is ocean themed and there is a cutting skills bookwith ocean stuff specifically.
Math manipulatives have such potential! Our favorites are magnatiles (if you can count that as a math manipulative), pattern blocks, tangrams, geoboard, and snap cubes. We find the snap cubes with round pegs easier to use than the ones with the different shape holes on each side. Beyond just having the manipulatives, there are a ton of fun activities you can print and use with them like mats for pattern blocks or tangrams that give you the picture to make. Teachers pay teachers has a bunch you can buy and print. Maybe a gift card to that site. You can also buy things like that on Amazon. Here is a pattern block one as example.. The phrase “task card” will help you search. Also lego task cards or legos at all! There are educational lego sets too.
Lakeshore Learning is a great website to check out for fun educational games and things of that nature.