This point is about only betting on what you understand or betting on advice you receive from who you perceive an experts in this field. To explain
I have bought shares in companies many times and let me tell you I have lost more money than I have made due to the simple fact I have bought companies I know nothing about. You speculate or dare I say gamble because the media makes out the mining industry is going through the roof or the banks are bullet proof! LOL how wrong could they be? In Australia they still say the banks are bullet proof and then in came the liquidators last week on Banksia! Totally out of the blue and millions of dollars lost. Anyhow I diverse...my point is, unless you have inside information (which is not legal) or you are getting first class expert advise which you pay for (pension or super) then don't bother buying shares. Exactly the same goes with Sports Betting.
I have in the past bet and failed miserably on betting on AFL, Rugby, Horse Racing, Tennis, Golf, Cricket, Darts and probably marbles! I have lost because I am gambling, I am taking a punt on an outcome I have no clue about. I am doing this for the sheer thrill of having a bet. This is fine when it is just for fun but they can all add up and massacre your betting bank at anytime.
To summarise it is vital you do your own research and learn to specialise in a particular market. It is physically impossible to specialise in all the markets listed above and for me I have chosen to just bet on Football unless I have expert advise (or follow a tipster). I take this even further by only specialising on a hand full of leagues. I would argue it is impossible to cover all leagues around the world. There simply isn't enough time in the day to do adequate research.
My final point is that of tipsters and why we exist. We can specialise in markets or leagues you cannot yourself and that is why you subscribe to us. I follow a Horse Racing and Rugby tipster for that exact reason. Tipsters should also apply the discipline required to be successful which in turn will generate you profits.
(I used to see this on share forums all the time referring to DO YOUR OWN RESEARCH. Anyone who posted to buy a particular share would sign off with this to probably make themselves feel better when the share price collapsed LOL)