Just a few tips to help you get through this:
Every $20,000 win in a Classic Game Solo will earn you roughly over a full level up, this goes slightly down the closer you get to Level 30.
Playing and beating the same family 5 times in a row by winning $20,000 will net you at least 4 level ups and drop to nearly 3 level ups the closer you get to Level 30. It pays to play against the same family over and over again. (You also win the car this way, which nets you an additional achievement).
Difficulty doesn’t seem to affect the total points gained, although I did not pay close attention to this. The harder settings just give the computer families better chances of stealing a board from you by answering correctly.
mossfan563 has been building a Google Doc of answers to help everyone:https://docs.google.com/spreadsheets/d/1CuqnF4ehkOvUsdKwMeh5...