For an off the shelf college basketball game where I thought I had a regular edge, I was betting $500 per game. For major conference stuff that was no big deal and could be done in one bet at one book (find best number, pull trigger). For smaller conferences most shops would limit you more than that, so you might have to bet it in a couple of spots. You also might wake up to $50 limits on any given morning, depending on your success rate.
I'm an an analytics guy, so my process for betting was actually kind of boring. I had a spreadsheet with power ratings, so I'd make numbers for every game before they came out, compare the opener to my number, if two teams I had strong conviction on were playing I'd immediately bet it...I'd dig deeper into the others, sometimes the market is right and I'm wrong, obviously. How the spreadsheet was made is probably more interesting. In the preseason, I'd use the previous years stats to assign a number to each team Big 6 + A10 + Missouri Valley (arbitrary but it took about an hour per team). Anybody can do that, of course, the trick in making the numbers "good" is being able to figure out who was a basket better or worse than they "should" have been the year before. What I was doing was finding outliers in certain numbers that don't actually represent a skill, even though most people think they do. My favorite example (that people still argue about) is 3P% defense. We all grew up with coaches yelling at us to defend harder/contest/whatever, so it's intuitive to think defense has a lot to do with 3s going in or not...but with very few exceptions it's actually random. A team that is otherwise properly rated by the market but has been extremely lucky or unlucky on 3s going in against them was a gold mine...for every team that you find a couple of points of value in vs the market, that's worth thousands of dollars. Sadly, you could use KenPom's data to make better numbers today than I ever had, get every team, and spend less time than it took me to rate Creighton in 2001. If I could pick one way that KP fucked me the most it was teaching people to adjust properly for tempo. We all understand now that having Florida State +5 against Virginia is WAY different than against North Carolina, but not many people were thinking that way 20 years ago. And that rat bastard showed everybody and for free. In the early days he actually adjusted this too much, and systemically overrated ultra slow teams.
My NFL style is a little more intuitive to people, once you explain the logic to them. Recovering a fumble is a pretty random event. Some crews call more penalties in the secondary. A team's SOS is better measured by projected win totals than last year's records (ESPN still fucks this one up every year). Third down conversion is dictated far more by how successful you are on 1st and 2nd down than by teams having vastly different ability to convert 3rd and longs. The other area I made money was by not overreacting to injury moves, that's almost universally overrated. If Patrick Mahomes misses a game and whatever warm body starts, I'd move that game about 8 points. People think "8 points isn't much, Patrick Mahomes is the MVP", but NFL teams are so jammed together that it's actually a shitload. Hence my Dolphins love last year. You can quibble with the difference between Josh Rosen and Ryan Fitzpatrick, I didn't even calculate it last year...I just saw the number come down and go back up 6 points different and immediately knew that was wrong. The fact that they beat the Patriots in week 17 to give the Chiefs the 2 seed capped my love affair with that team.
Full disclosure: I was successful but never moved worldwide lines. That's some baller shit.