It's funny you know.
When I first started gambling it was very straightforward, just like you said, I wanted to have some low-risk strategy that allowed me to bet everything on short-odds results (for me it was total goals 1 or greater, around 1.05-1.10), and over the course of time I would be able to build up a small stake into a large pot.
Funnily enough I did pretty well to start with, turned $20 into 50 (but then lost it) a few times, always thought to myself "ah fuck it I only lost $20" but then got impatient and next time would start with $30 because I didn't want to have to wait so long, only winning $1 at a time wasn't good enough. Then because I had lost a few initial stakes I thought I would recoup the money by placing a larger stake on a slightly longer (but still pretty short) odds result, say 1.25-1.30. Needless to say, a few of those missed and before I knew it I'd lost a few hundred $. As a result I realised that I didn't want my life to pan out like that, and that gambling was ruining my love of sport, and that actually the best thing for me was to forget about sports betting and simply focus on enjoying sport as a spectacle.
And ultimately I realised after the event that the biggest part of the problem was that I didn't see the money I put into it as a write-off (which I should have done), I saw it as an investment, in the same way that you described: all I need to do is increase my pot by say 10% a month. Actually the way to look at gambling is like buying a pint, you pay x amount and the value is what you consume, rather than the prospect that you might get any money back (for this reason I can quite happily go to the horses or the dogs, I know if I spend £20 there then it's because it is part of the entertainment, if I don't get it back I don't care). Whereas when you try to "build a system" where you are aiming for a specific % return on your investment, then over the long run you will lose every time (unless you are somehow cheating the system).
The reason for this is simple: Bookies make their living by offering odds that are lower than they should be for the inherent risk involved in the event.
Anyway, to get back on to why I started this thread with a "it's funny you know". I have avoided sports betting for the majority of the last 2 years, except for a couple of occasions - namely, when the bookies throw in a free offer. When I stopped gambling online, I didn't close my accounts, so from time to time I get an email saying "if you deposit up to $X, we'll match 50% of your deposit as a free bet". I got one of those a few days back, and replied to the email asking for clarification that I was allowed to deposit my own money, claim the free bet, withdraw my own money (without gambling it) and still use the free bet.
The guy replied saying "you're free to do what you want with your own money, but withdrawing the funds after depositing would be missing the point of this generous offer". My heart bleeds for this poor charitable organisation who are relying on the goodwill of gamblers to make ends meet.
Anyway, I realise that this is probably a major downer on your original post - I would be lying if I said that I was sorry for that. IMHO I agree with the guy who replied "delete this thread, save yourself, and forget you ever heard of a thing called gambling".
If you are still reading, and still want to go ahead with your plan, then you could try something extreme, such as no hat trick (super low odds, though RAWK will take the piss out of you eternally, as there was a guy on here a while back who tried the same thing, and pretty much his first game he called that then someone scored a hat trick). Otherwise, I had some success with "1 goal or more" markets, the odds are usually 1.03-1.15 (as extremes), though you will need a lot of discipline, as they only increase in value very slowly (and set yourself a limit after which you cash in). Alternatively you can pick a sport where it is head-to-head and the draw either doesn't exist or is extremely unlikely (i.e. tennis, or most American sports, I used to do it on Aussie Rules).
[As an aside, I had a couple of mates in Oz who did the game where you start the season with $100 and every week bet it on a short-priced favourite, in the range $1.20-1.50. They got through 9 weeks and had turned their initial stake into $3000, all of us told them to cash out and spend the money on a holiday or something, instead they said "Nah it's all good, there's one this week that's totally nailed on, we'll do that and then maybe think about it". Anyway turned out that week that Richmond (perennial whipping boys) played away at Port Adelaide, instead of getting smashed they took the lead early and it stayed like that for most of the game. My mates started off calm "Oh Port Adelaide are bound to come back, Richmond will choke" etc etc, as the clock went on the margin narrowed but with only seconds on the clock Richmond were still up, my mates were just sitting there looking sicker and sicker. Suddenly out of nowhere one of the Port Adelaide players took a massive pack mark (i.e. jumped through a ruck of players to catch the ball cleanly) then went on to score the wining goal with seconds left. I said to my mate "Wow that was lucky, surely you must cash out now", but by the next weekend they had gone and stuck their whole $3000 on again. That week's pick got rolled and they lost the whole lot - when I asked him how it felt to $3000, he said "nah not really we only started with $100, over the course of 10 weeks that's only $10 a week"].
What I would say is if you really want to use this as an investment strategy, work out exactly what your target is and when you reach it, cash out. Otherwise it is very easy to get sucked into the temptation of just putting on bet after bet until you eventually lose. Also, be prepared for the feeling AFTER every results comes in - if you have won, there will be the voice in your head that says "I should have put more on, it was so obvious", and if you've lost there's the voice that says "Shit, now I need to make it up, next time I'll just start with a bigger stake so I make my losses back". If you can avoid BOTH of those over the long term then you're doing better than I ever did.
Hmm I'm suddenly feeling like I should have put this in the thread started by rafas3leggedtable.
Whatever you do buddy, good luck with it