hi, i will advice you the same thing as Ricohflex. Let me explain why:
1. Like you, i baulked at electricity and used a tupperware + thirsty hippo/silicon beads setup. I was naive then. Having to periodically change/'recharge' the silicon beads can be frustrating. You will sooner or later spend more than buyer a proper cabinet , trust me.
2. How much to put it: Get a good hydrometer and use it to measure the %RH as a guide. The tupperware size decides this.
3. After 1 yr of tupperware usage, one of my lenses kena fungus. It was a case of I did all reasonable steps - clear the lens after use, dry properly and keep in tupperware with proper change of silicon beads. Paying to clean that lens erased all cost savings I could ever hope to get.
4. Switched to a good dry cabinet with recommendations from the seniors here, and now i'm never happier. Go count the electricity usage + cost of cabinet and you will know that u will save in the long run - financially or peace of mind.
I use MFT and i swop between my cameras everyday too
Thing is bro, u ain't gonna be bringing out all your lenses everyday too so there will be equipment in long term storage.