I'm working on a project for a client that is currently using Excel to generate numbers for charity donations based on a percentage on income linked to each client.  I'm not sure where to begin to create a system in Zoho Creator.  But here's what I have so far.

I have a set of forms like charities, customers, payments, payment reports.  When I enter a payment into the payments form, I need to push those numbers into another form, do some math based on linked entries.  The end result needs to be a monthly or quarterly report based on the payment recieved for each piece of equipment

Attaching current relationship diagram.

Where do I begin?  I'm not proficient with scripting so I'm really starting from scratch if I have to get heavy into Deluge Script.