Complex dashboard using presenters and/or service objects
There is a lot here and without diving into the pattern based approach, my first question would be have you considered using rails scopes? Maybe that answer is overly simplistic, but using scopes would get rid of a lot of your reporting methods and make you be able to do something like: 

Spendings.last_month
Results.last_month


And speaking of Spendings and Results, it sounds like you may want to create a rails class or model for some of these items (like Results and Spendings and Expenses) instead of just querying them from a dashboard view? I have some tableless models in my apps that are used for reporting purposes. It seems like a much cleaner approach than having a long dashboard controller doing the querying for you. In that same vein, another data / reporting centric approach that isn't rails specific is to create reporting tables (these could be rails models) that are divorced from the transactional data just so you aren't querying reports from the live system which can lead to performance hits for both users on the transactional side and the reporting side. 

Rails is very "flat" from a traditional 3rd normal form database architecture, so it isn't much work to create reporting tables.... Just some thoughts. Good luck.