I do remember level 5 being a little tricky, but it wasn't terrible. All it really needs is some market research, math, and a bit of farming.
I made a Nartian Rock, 2x Classilke, 2x Bacon Capes, and a metric butt-ton of Moon/Sunstones, which also helped me through level 6. I didn't mind the extra material and crafting costs as long as I can use the product in another formula later on (for example, the Moon/Sunstones and Classilke). On that same train of thought, I also made 2x Meat Clubs and 2x Cupcake Confections at level 4 because I saw that I could use them in the Bacon Capes and Biancamellas respectively.
I don't know if you'll use the Moon/Sunstones later for backwings, and judging from your post, they're probably out of the question. Classilke is unlikely because the Purple Flies it needs got inflated along with the other bugs. Bacon Capes are also unlikely because there's only one very expensive Bacon Bits on the MP.
I did some quick 3 AM sleepy math for you, and it seems like your best course of action is to make 40 level 4 formulas. Meat Clubs use only Sapphire Cache components and gold shop items, so they're easy. Costs roughly 170k to make one, so 6.4 mil estimated total to get to level 5 making only Meat Clubs. If you don't mind spending a little more, you can make as many Nartian Rocks as you can and then fill the rest out with Meat Clubs. The most expensive part of the Nartian Rock is the Holy $#17, which costs about 2-3 mil. You can easily farm the Music Notes in zOMG, which by the way, is the same deal with the Kokeshi Dolls. They're inflated, but you can easily farm them. Mute the game, put on some good music or a TV show, and go to town on them.
Good luck.
TL;DR: make 40x Meat Clubs for the cheapest way to get to level 6.
P.S. I just scrolled down further in Lei's level 5 Formula List, and I remembered something. You can also make the Floating Angel/Devil Imp Potions. They require a little more legwork than the Meat Clubs and are a roundabout way of doing things because you need to craft some lower level potions first. But since you get 2x level 4 and 1 level 5 formula out of them, one Floating Angel/Devil Imp Potion will give you 24 exp. This means you'll need to make only 7 of them (rounded up from 6.67) to level up. Based on my old records where I made a potion for a buyer, it costs roughly 1.8 mil per potion. It'll cost you about 12.6 mil to level up through Floating Angel/Devil Imp potions. If you want to go with this option, I'm sure Checkmate and Pomy would love to get rid of the formulas in their
[thread]. The rest of the ingredients come from caches or gold shops, so that won't be a problem.
EDIT: If you're considering making a Glacemella in the future, you can also make 10x Candy Mountains somewhere in that jumble. Costs about 480k to make one, and you'll need 10 of them for a Glacemella. So yeah...you have a lot of options.
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