The educating and entertaining your preschooler might be right up your alley in that case. It has milestones and lots of cheap activities with household stuff.
At that age I had a fabric box for my DD (just random offcuts and stuff like scarves). She used to like packing and unpacking that and I’d group them by colour, hide things under them, arrange them and use prepositions (“where is the green scarf? Point to the one next to the green scarf” etc), talking about spots and stripes, show me the one that has the same pattern as this (I’d drawn the spotty pattern on some paper). We did some basic counting as well, and we danced around with them to music. We also wiped various different body parts with them, or asked her to “wash” mummy’s hand, foot, hair etc.
If there’s something that he’s got that is simple and he really likes you can do soooooo much with it. My DD is now older (2 and 4 months), and her current obsession is an easel with a whiteboard (her obsessions normally last about a month). So I try and do lots of different things with that. So I got pens with screw on lids to make her practice a turning motion with her wrist (something they are supposed to learn between age of 2 & 3), if she wants to have another pen she has to say whether she wants a big one or a small one, what colour etc, she has to ask in a proper sentence and say please and thank you (if she doesn’t do it properly I look sad and say that I don’t understand, “do you mean, mummy can I have the blue pen please”? And then get her to say it back to me). Sometimes I draw something and encourage her to name and trace over the shape (circles, straight lines, she can’t do much else yet), or I draw words and ask her to point out the letters and what sounds they make.
I think the big trick is not to buy anything new at all, but just find one thing your kid likes and really go to town on it with them. You can do so much with one simple thing, and they learn loads more than with having lots of different toys. Plus, so much less tidying up for you!