For the short term goal you should aim for the classic Hinata, Sasuke, and Sasori lineup. Get Hinata and Sasuke to 3 star, and there also should be cards on the bottom right that says recruit click that and use free draws to get sasori.

For the long term goal SAVE COUPONS don't spend em at all.

Save About 11-12k coupons so you can get ninjas like Kakuzu [Earth Grudge Fear] and Naruto [Sage of the Six Paths]. Along the way you will get ninjas for free like konan, Asuma Wind Blade etc.

So, ill go for the 10 scroll, Naruto chest (the one in red) so thats where Sasori drops.
-Ye im thinking on saving coupons to get Kakuzu EGF; Naruto S6P i think its currently on the event in the wheel of fortune, but i only have 720 coupons.
BTW in the Heavenly path chest (the one on the right next to the red selected one) Windblade asuma drops, aswell as Guy and some Pains, and also Hashirama) ins it better? and maybe sasori will be a common drop?, since on the Scrolls/seal chest i got Zabuza (on the far right to narutos chest).

Btw none of the Lee works?

Also found this page, it recomends some basic lineups but since its from 2018 i dont know if theyre good, these are f2p

https://narutoguides.com/team-build-f2p-lineups-earth-main-crimson-fist/