1. Hold onto your TEs like your life depends on it. Collect, collect and collect.
2. Trade Stray Cat for 10-15 TEs.
3. Train and collect bear at 10-4. Make that bear to lv10 (need 16 1* in regular time and 11 1* in enhance bonus time), and feed it to 4 when you collect bunch of them. Well, this is my method anyway.
4. Max 4*. Now a days, you can get fresh 5 for 3 max 4*.
5. Max 5*. I got Abel and Ana in that way, got Monica with max Ana, two max 5 and two max 4 (thanks for that deal), and Nina with Abel and Mata.
It will take long, long time and mindless boring grinding...
Of course, if you don't want to do that, just buy your way out