Average Minimum per Month

Hello guys, 

Please help with the following: 

I have 2 tables, transactions and budgets

Transactions:

And budgets:

Considerations about budgets:

Everyday 1 entry with a new budget is created per user, for reference, when multiple budgets exist on a given time frame for the same user, the last one is to be used if not a more specific datapoint exists. (last of the month, last of the week,last of the given period)

What i'm trying to achieve is the following:
1 - The average minimum balance per month. So every Month, each user has a minimum balance, i need to calculate the average of that minimum balance amoung all users, per month. (should be a value per month) 

2 - have the same average calulation but instead of absolute value, the percentage of the users Income.  (should be a value % per month) 

Can you please help me with this request?

Thank you