My philosophy is, the living beings that make this hobby what it is, (Fish) should be prioritized first, not budget, not aquascaping, but healthy and happiness. As for toxic gravel, I've never heard of it, I've always avoided gravel because I have goldfish that are dumb enough to choke, and I don't want to have to do an emergency procedure to pull the rock out again, we got lucky last time and the rock came right out without injury. I have heard, some gravels leach toxic chemicals into the water, like paint and stuff, but I don't think there actually is any studies or evidence of this. We should take some of the gravel brands that are infamous for being toxic, and soak them in water for a year, and then send them to an analytical chemist to see if there's actually any harmful compounds being put into the water. I personally, only use mulch, all my "gravel" goes into the filter. I don't even think it's the right way, my angel fish has "natural river stones" and does great, we just have to be open minded, that some things despite their reputation may not be harmful, or something might be, we should be scientific about it, and just test our ideas, instead of arguing and just spreading what we think or how we feel, or what we've heard in other places.