Many people may be wondering what is the best way to prepare for Madden Mobile 26. Unfortunately, the answer is "we don't know for sure". Although we know what is and isn't carrying over, we don't know what value the items we can carry over to Madden Mobile 26 will have, and it's unlikely that we will be given this information before launch. So defining the optimal way to spend resources in preparation for the new season is impossible at this point.
However, we can make some educated guesses based on past history. Below I have detailed how I am preparing for the new season, along with rationales. Keep in mind that this is just a guess, so follow at your own risk. Also, regardless of how you approach your own preparations, most likely anything we carry over will have very limited value. So if the path you choose ends up not being the optimal one, it shouldn't set you back by any significant amount.
We know that Madden Cash will carry over to the new season. I would not spend any more Madden Cash in Madden Mobile 25, as the value of MC will be much higher at the start of Madden Mobile 26 than anything that it can be used for now.
Coins, league tokens, and trophies will NOT carry over to the new season, so it's best to spend them now on items that will carry over. For coins and trophies, that means player packs - either Pro Packs, All Pro Packs, or Madden Packs. Which packs you ask? Technically Pro Packs have the best statistical return, but the difference is negligible. I have been doing All Pro Packs just because it's fewer finger taps and provides a good balance between guaranteed return and potential. But it's not a big enough difference to worry about.
For league tokens, these can be spent to get either more coins for players, or to get play tokens. I personally have been using league tokens to get more play tokens. Although play tokens themselves do not carry over to next year, they can be used to get plays which will give a bit of a head start next season; see below for more details.
Play tokens and acquired plays will NOT carry over to the new season. However, you will earn a number of play tokens next year based on the plays that you acquired this year, so it's best to spend play tokens to get plays anyway. Unfortunately, we don't know what the ratios will be, so it's impossible to know what the most optimal way is to spend play tokens. There are a few possibilities:
Buying the cheapest plays in the store first will be the most optimal path for #1 and #2, while buying the most expensive plays in the store first will be the most optimal path for #2 and #3. For #4, the optimal path would be to get the plays with the highest value for (play token cost / PBB cost).
I am personally buying the cheapest plays in the store first. The rationale for this is that I think the likelihood of #3 or #4 is low compared to the first two, and since cheapest plays is the most optimal path for both of the first two options, it seems like the safest choice to me.
While Season Team Training is returning for next season, our current Team Training Points will NOT carry over to the new season, so it's best to spend them now. That said, I personally wouldn't spend coins on Season Team Training at this point unless you only need a small amount to get another player reward. So I would only spend Team Training Points on boosts between 6 and 10 so that you don't need to spend coins as well.