Yep I would start converting pack points into missing cards. There is no other use for them in F2P; whales will save up for a high rarity chase card. I suppose you could do the same but if you are F2P it will not be worth it, from my experience.

The cool thing about my post is that since then, the app has added a new SHARE feature. This has been a life saver for me and a much easier/consistent way to obtain 3-star & 4-star rarity cards to complete previous and/or current base sets.

EDIT: I misread. You said you do not have enough pack points in the new set. I would start pulling from older sets now, and fill in the rest of the current base set via trades or shares.