You probably should stick to published formulas as written for now. I don't think you have the experience yet to be able to objectively decide when substitutions are appropriate, will work, or are safe.
It looks like you'll need to make a small investment in chemicals to be able to make much of anything. Probably the best way to do this would be to sit down and decide what you'd like to learn how to do or devices you want to make. Right now you're basically limited to black powder and charcoal based compostions. This really isn't a bad place to be. You can learn how to make many things with what you already possess. They're the easiest, cheapest, and most forgiving types of compositions generally.
If I were in your shoes I'd look into getting atomized aluminum or coarser magnalium (-200 mesh is most versatile IMO). The 600 mesh stuff you have isn't good for much actual pyrotechnics. Both the aluminum and MgAl will make glitters. The coarser MgAl will also be an ideal fuel for colored stars. The green formula above will make a recognizable green color, but in my opinion are overall kind of shitty. You also need to remember that metal fueled stars are not easy to get lit sometimes, so you'll need a hot prime to get them going. These can be nitrate based, but many of the most effective are pechlorate based. Barium nitrate does lend a unique effect to some glitters however, so it may be worthwhile to look into. Barium carbonate is also an effective glitter delay agent for white glitters.
Another thing to look for is iron/steel or titanium. They can often be found as turnings or industrial by-products. These compliment BP based effects well, and are simple ways to really open up your available effect range.
If I were you, I'd focus on learning the techniques and learning how to make effective shells, mines, fountains, etc before worrying about adding colors.