Check daily rewards and your starting balance
Open the daily rewards and time prizes shown in the current update. Account for those rewards before changing your inventory. If you try a developer-listed code, record whether the balance changes before trying a second one.
Keep a reserve of items you intend to retain
Separate the items you want to keep from duplicates you could give up. Before confirming a change, read the displayed cost, outcome and odds. Check where the item goes on failure and stop if the interface is unclear.
Compare tiers on the same type of item
Read the cost and displayed chance for each available tier using a comparable item. The multiplier describes the potential increase in rarity. A single good result does not tell you the expected outcome of repeating that tier.
Set a stopping point before you start
Pick a small limit in the game’s virtual currency before trying upgrades. Review the items and balance you have left after each attempt and stop when you reach your limit. Check the current rules before using an old recommended upgrade order.