If you have a regular job, don't worry too much about bankroll requirements for low live stakes yet, just decide how much you can afford to play with and enjoy it. Many poker players started out like you and built a roll some how. You've already decided you can afford to replenish $100 a month. I don't know what games are available to you, but if you can find a regular $50 weekly tournament, just play that every other week and work on improving your game until you start crushing it, then you'll have a roll that you can invest in more serious and regular play if you choose. That was pretty much how I got into poker and became a more serious and regular winning, but amateur player.
The other thing I highly recommend if you have the availability where you live is playing online satellites to live events. Learn good satellite strategy and play satellites regular and you can soon find yourself going on some really fun adventures travelling around parts of your country or even the world you never even considered going to and all you need to pay for is transport and a hotel. Again, this was something I did a lot when starting out and I had some very nice wins for a very small investment.
Over the years I learned that poker is much more enjoyable and even profitable if your aim is to have fun, learn and travel as a hobby rather than just trying to make money.
I hope this helps, good luck