Hi PR
IMO a good newbie recipe is a STRONG recipe.
It doesn't really matter much what is in it as long as 1/3 to no less than 1/4 of it is Portland cement.

Recipe #5 will work but your sand mix should be fresh and you have to keep your water to a minimum for maximuim strength.
ALSO some sand redimixes have aditives that retard or speed up the curing process depending on their purpose, so you have to know what you have.

My second try with the sand mix came out ok/useable but still seems to have some of the crumbliness that my first (failed) attempt had. The two things I've made not using the sand mix (portland/sand/perlite and portland/sand) came out great!

I used the sand mix recipe because I had the mix and knew it was good a month ago with making leaves. Just wanted to give it a try and see how it worked. Got into a mess instead - two precious glass lamp globes, two pots and a stepping stone - all junk. Well, I am washing out the globes, and I'm going to rescue all my neat beach stones from the one globe if it kills me.

Time to get the quality materials. I think I can get Portland cement at HD. What is the right kind of sand? I read that play sand is no good. I'd like something white - is that available at HD too, and OK?

I found white sand at HD back with the landscape gravel. It seems to work well for the two projects I've done so far.

Playground sand is OK.
I have made some nice stuff with it and use it quite a bit.
But in my opinion I find that all silica sand and sharp mortar sand used by brick layers to be superior. They have more sharp edges, more bite where as playground sand is more rounded.
They don't cost much more than playground sand either.
In fact brick layers sand is cheap but you have to usually buy it in bulk.