I made a previous post asking for general advice on some cleanup, cheap substances and similar stuff. After reading some very helpful responses I realized there is much more to this than I first thought and was wondering if if anyone would be willing to chat with me in dms about just general cleanup advice, substance advice and stuff like that. I am doing it with someone online where they will be the ones getting messy for me and I am trying to do everything I can to educate myself to make the process of cleanup and such very easy for them and would love to people who are more experienced in it to have a conversation with in order to help educate me so I can help her.
For cleanup, the only real advice I have is to use plastic sheets to cover any surfaces that you're near (as well as any drains, if you're using anything that could clog them).
As for cheap supplies though, I do have a few pieces of advice.
For gunge, I never buy the specialty powder from sites like MessySupplies. Nothing against them, I'm sure it's a great product, but you can get a reasonably good experience from just a package of Xanthan Gum, water, and some washable paint (PLEASE MAKE SURE IT'S WASHABLE PAINT BEFORE YOU COVER YOURSELF AND YOUR HOME WITH IT. Try putting a small amount somewhere on you that you can hide easily, and then after drying see how easy it is to get off of you and if it will stain). I usually mix the Xanthan Gum with the water at a 1% gum to water weight ratio, but you can adjust based on your preferences for thickness. This site (http://superpants.net/gungerecipe.html) covers it pretty well imo (You will have to click that you accept that it's not an HTTPS site, but since you aren't entering any information there's no worries about data stealing). The Xanthan Gum can be purchased at either Amazon or Walmart if you're American, if not, I'm sure somebody else can help you figure out where it's available in your country.
If you're into things like cake, then my advice to you is to use boxed mixes, rather than storebought cakes. If you really need the look of the storebought cake then it may be worth it to you, but if all you care about is that it's a cake, a box of Great Value cake mix is just over $1, a tub of frosting is just under $2, 12 eggs are just over $2 (this one will vary based on your area for sure), and you'll only need 1/2 cup vegetable oil so I won't be counting that into the price. Compare that to a $20 sheet cake, and you can save a ton there. You can also get more of of a single cake by cutting it into slices and then using it that way rather than just all at once.
For pies, the math can work out to be not worth it depending on the pie, so you may want to do the math yourself on the prices of the ingredients vs premade pies. Frozen pies are also a valid option here, I haven't tried them myself, but many users here swear by Marie Callenders frozen pies (obviously make sure they're completely defrosted before you use it).
I've mostly talked about sweet here, but for savory, store brand can result in a huge amount of slop for a small amount of money. If you have a Sam's Club membership, 114 ounces of Member's Mark ketchup is only $5. If not though, Walmart has Great Value ketchup at 64 ounces for $3, which works out to be a bit more expensive, but not by too much (and you do get a bit of extra ketchup so it's not a total waste of money). Costco is also a valid option here, but I've never been to one and I don't think I can look up prices for all items online, so you may have to go to a store in person to check it out if you prefer Costco. Pretty much this entire paragraph will apply for all sauces, whether it be salad dressings, mayo, pasta sauces, etc. Pretty much just go store brand and you'll find your costs cut in half pretty easily.
Good luck, and hope this helps!
Edit: Just realized that you said you already asked about cheap substances. Whoops, I'm stupid, lol. Going to leave this here in case this helps, but sorry I missed the real reason for your post.