Some cheap substitutes for perlite include sand, horticultural grit, gravel, pebbles, etc. But unlike perlite, different types of stones can be too large, so you might need more time to find the ones that fit your needs. Also, there are specific sand types suitable for gardening, such as horticultural, builder’s, and river sand, so use them instead of beach or play sand, which will only compact the soil and lead to waterlogging.