You should save to buy more powerful cards. 4* go from 250-400k per 5* from 2-15mill 6* are priced in a class of their own. basic packs can merit 3* cards as the rare if there is a chance to obtain 4*+ it is not on the net or shared publicly.
Edit: also 1-2* cards are not really garbage lol you can sell them to help save for better cards or use them to enhance your 3*+ cards
Note: level 20 3* cards are worth any-ware from 100-150k making you able to save that money for better cards more easily.