I decide to pay for the things that I want and the things I am prepared to take a chance on. In the early days, my Gold went on garage slots and permanent camouflage. Since the changes to camo came along, I now rent for 100 battles even on my favourite tanks as WG are fond of [edited] up, balancing, nerfing - no. [EDITED] UP my favourite vehicles such as the VK 3601 H, and several LTs. Not to mention the SPGs I sold after the great 8.6 and replacing the T57 tier II.
I started paying some Gold for crew training for SPGs for loader and gunner, but I do use gold more often now. The main reason for this is having many redundant crew members from abandoned lines who are not only changing vehicles, but vehicle type.
I have bought a couple of Premium vehicles directly for cash- the Cromwell B and E25. The other two were bought for Gold (Churchill III and Even 90). All of the others were gifts/prizes although I bought one token for the T25 Pilot.
I bought loot boxes last year as you do pretty much get their value in Gold and I needed some. I got a few Premium vehicles and the Skorpion G (basically) free.
I won't lie. If I chose to, I could buy every Premium tank available and run full-time Premium account. I don't, because I don't want to. Those particular things have no special attraction for me. So I spend what I want to, WHEN I want to and that is how I help to keep the game afloat. I am just in my eighth year and have easily spent less than £500. One major PC game a year at full release price would easily get close to what I have spent. If they shut WoT down tomorrow, I have no regrets.