Step1
If you're the leader
--------------------
You'll have to assume the second place contestant will bet their whole score so double the amount the second place contestant has, subtract your score from that then add 1. Here's how it would look:
Leader $10,000
2nd place $7,000
Double second place score: $14,000
- Leader's score$10,000
Add $1 to be lone winner$+1
-------------------------------------
Correct wager $4,001
As long as the leader gets the question right, they will win no matter what the others do.
There is no point in going for the tie. You're basically giving them money they didn't deserve!
Step2
If you're in 2nd place
-----------------------
You either bet all or $0. It all depends if you can win by default meaning can you win the game if the leader bets the required amount to clinch a win no matter what.
Example:
Leader:$10,000
2nd place:$8,000
The leader should bet $6,001 so the 2nd place contestant can win by default if the leader gets it wrong while the 2nd place contestant bets $0.
When it's mandatory to bet it all
---------------------------------
Example
Leader $12,000
2nd place: $7,000
The leader will most likely only bet $2,001 to clinch the win so even if they get it wrong, the leader will still have $9.999. I don't think it's worth it for the 2nd place contestant to bet just a portion of the $7,000 so they might as well go all-in since if they get it wrong, they're going to lose anyway.
Step3
3rd place strategy
--------------------
Lots of contestant have won from this position since the other 2 in front of them usually get the question wrong and they end up cancelling each other out.
Bet $0
-----------
Example
Leader $10,000
2nd $8,000
3rd $5,000
The leader most likely will bet $6,001, the 2nd place contestant will most likely bet it all so it's a good strategy just to let those 2 fight each other out. The only drawback is if one of them chicken out and bet $0 themselves but usually they bet the former.
Novice 
