Which you think will make one improve the most, daring to do wild play, gambits and sacrifices? Or playing to get the best possible result all the time? I know you don't make sacrifices out of the blue like this, but things like the muzio gambit and such?

I would say consistent and solid play is the best. I prefer to play a low-risk style and try to slowly accumulate small advantages and grind them out to convert for the full point.

But I don't mean to win the game, I mean to improve.

I guess it depends what they've already learned. I've played the Muzio gambit in one of my games on here to try it out and see what I can achieve with it. I've never really played gambits before so it's new territory for me. I suspect that's true for most people but there will be some who could do with learning to grind (also true for me, I get impatient).

It may depend on your style. If you like to be aggressive then go ahead with risky moves looking for tactical combinations. If you prefer to hold a solid position, then try to get little strategic advantages. You should test and discover which style makes you feel more comfortable on the board.