Let me tell you that I totally understand this mindframe because it kinda was mine, except that I was never one to be afraid to throw money at a new investment.
I spent a lot but I learned so much more, so I never consider it a loss.
For everyone trying to build a list, congrats on understanding that list is important.
There are many who make a killing without a list, but that's not the point of this thread.
However if you think you can build a list of any signifigance for $100 or anytype of one off payment you are kidding yourself.
building a list is an ongoing business and the only way to do it without going broke is if you are making money while doing it, and yes it's possible I do it as well as many others I know.
When you are getting paid to build your list, the sky is the limit.
You need to pay for an autoresponder, and traffic to your squeeze.
You could try to set up a blog and get organic traffic but that is a very long term game and still comes with its own costs. webhosting, domain name, and tons of time (time is money). Not to mention you will probably pay for seo services and stuff, ive been there.
The other option is to send traffic directly to your squeeze, which also cost money for the traffic. Unless of course you are swapping traffic, but in order to do that you need a list.
So don't hold yourself back with notions like I want a big list for cheap.
It will cost money and will take ongoing effort. Not necessarily alot of effort but consistent effort.
The magic bullet.
Make your list building efforts profitable, once you do that. You are more than half way there.