How to calculate ROI?

Question

CRM

Good afternoon.
When I started working, I led all the clients in a regular Google spreadsheet and calculated the return on investment (roi) in it, I had only one channel for attracting clients - Yandex direct. In such a table, I drove in the initial data in the form of spending on advertising and the results obtained - clicks, leads and all other results by stages of the sales funnel. And thus I understood how much it costs to attract my average client, riches saw at every stage of the funnel. For example, a click - 10 rubles, a lead - 300 rubles, an application - 600 rubles, a sale - 1200 rubles.
With the development of the business, the analytics system improved and one fine day I added the amount of the trace to my table, registered the profitability, divided the indicators and got the ROI, it was a bit inconvenient to track each transaction separately, I had to write the sum of all transactions in one cell, but I understood the final result.
The problems started when I added a new acquisition channel and all of May the detailed analytics went to hell, I tried to improve the table but my attempts were unsuccessful, now I want to improve and move to a new ROI calculation system, taking into account the many acquisition channels, the ability to analyze all transactions separately, well, it would not hurt to start the analysis starting immediately from the keywords. The main criteria are the simplicity of the interface, CRM and ROI analytics in one system, of course, so that it is not very expensive...
Please tell me the options...