What a question. How/where do you get collectors?
Haven't you heard? You simply get them at Wellingtons, the collector supermarket. They run about $299.99 USD.
Well, sorry, I couldn't resist.
I started with my own circle of friends. I wrote a newsletter to them asking if any of them would like to purchase any of my paintings. I invited them over to my studio for a get together and asked them all to bring at least one friend of theirs that I did not know.
Now, most of my friends could not afford art, but I started my work at low prices and I offered payment plans.
I gathered all the new people's addresses and then they also got newsletters, and I always asked if they knew of anyone who might be interested in my work to connect us: either bring them over or give me their address so I could add them to my list.
After some years, my list grew from 10 to 500. After 10 years, 500 to 1000. after the internet came along, the next 10 years I gathered a few thousand more. People opt out, and new people join. You win some, you lose some.
Patience, marketing, promotion, exhibitions, open studios, lots and lots of personal communication, commissions, sales, making it possible for someone who really does love your work to own it... you have to build your house carefully and kind of slowly, but it won't take forever. The internet makes it SO much easier. You'll see.
I hope I've helped and you didn't mind my little joke.