Hello!

In my opinion, it is best to get other Element cards first before getting the Stats/Debuff cards (if you are using different teams that has different P1s). Like what I did to mine, I started maxing my Temari card since Assist Cards came out during the days where Jonin Minato was still on the top metas, followed by maxing my Gaara card and Mei card (For my Kushina and Tenten teams) and then Onoki card when I completed breaking my Kakuzu. Tenten is a good choice also too but having other Element cards ready is much better. Minato card is also a good option especially if you are fighting someone with close initiative count where using Minato card can overcome the gap and gave you an advantage.

Well your goal should be to unlock them all. Not to use them but to level them with potions. Thats the best way to gain power.

When you get a new card dont waste cultivation pills unless you are planning to use it. Some cards are really good for specific teams. Like for kakuzu you should use Onoki card. Or for Kushina or Naruto 6p you should be using Gaara card. Cards like that should be maxed with the pills.

If you change teams a lot but you dont have cultivation pills to level all cards then Tenten is a good choice. Critical is a good offensive and defensive stat.

But as i said you should try to get them all. And your power will increase fast