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.