weak calling hands

You could try a strategy where you call with every hand if noone has raised, but I don't recommend that if you want to win as much play money as possible. You might want to do it to practice playing on the flop with weak starting hands.

Here's a pretty loose pre-flop limping strategy. You should probably play a bit tighter. If players frequently raise preflop at your table, you should definitely play tighter:

Call with any suited cards except T6, 95, 84, 73, 62 and worse (smaller kickers with your highest card).
Call with any offsuit hand except Q8, J8, T7, 96, 85, 74, 63, 52 and worse.

I don't like 4-gappers, but I might limp with offsuited three-gappers from the button or small blind if I think I'll get a cheap flop. Let's just use the mentioned limping strategy now.

If you want to play a lot of flops, try to find a table where there's not very much raising. You can use this strategy at that table. At a table with a lot of raising, you should fold anything that isn't

1) a pair
2) suited connector or Ax suited or
3) two high cards (ten or higher).