I found a good tip is to work your way up, 3 a smal jump, then 3 a medium jump, then 3 a large jump.
If you can't perfect a 3 on like a medium jump don't try it on a large jump.
But sometimes your mountain only has big jumps (not enough progression)...
So evetnually your gunna have to throw it on a big jump.  A good trick to work your way up is to act like your gunna spin off the lip  and just look behind you at the horizion and then back to the landing.  This way you get the feeling of doing a spin (take-off, not seeing, landing) without doing one.  Also, trying different straight air grabs helps to gain blance (and confedince) in the air.
And chances are, on any spin that your not corked or inverted the consequences aint so bad even if you land awkwardly.
And by the way, I'm not an expert, I'm in a similar situation, and this is my plan.