To stack multiple boosts
1) Click on the 10 minute boost button.
2) It will take you to battleon.
3) As soon as a boost appears click the X next too the boost button on the bot manager
4) Accept the boost
5) Repeat steps 1-4 till you get the desired number
Alt Method
1) Do the above steps accept when the boost appears immediately click accept
2) Continue doing this until you get the desired number
The only difference is that the second method has a much more likely chance of disconnecting you and the boosts will appear in the bank.(Unlike the first which will stay in your bag)(although you still need at least one bank space) It wont show that you have multiple boosts but try deleting them and you will see that you have way more then 1
Simply clicking the boost button and hoping that you get a bunch won't work it will just get you disconnected or disappointing XD