whats the best and cheapest way to take a nova / tyrant item to 5 stars?

I know there are no booms, but they cost near 2B each in scania. I know there are protection scrolls but they costs around 300m each and thats still way too much for my budget. Even star force costs too much and is too luck based for what i can spend so whats the best and cheapest way to take a nova / tyrant item to 5 stars?

Thank you.

You can buy two Superior Wards per month with Reward Points (which you get from bossing or from Star Planet Mini-Games).
If you have a 5-star enhancement scroll, use that with a Superior Ward and a Guardian Scroll (also available in the Rewards Shop; keeps your 5-star enhancement from disappearing if it fails, so you can try again).
If you don't, use an AEE for the first star (it's 100% success), and then Superior Ward and more AEE. It's slow, but if you've neither NX nor meso it's pretty much your only choice.

I've had good experience using a 2 star enhancement scroll and then star forcing to 5 with my tyrant items. On 3 of them, it cost me less then 500m each to get to 5 star (including 2 star price). From there, superior wards in the reward shop + aee got them to 7 stars. Nova's are not really worth using anything but ee's on.