If you are a speculator, who is looking to mine coins that have future potential, then do your research, pick a couple solid coins that look good and find a reliable pool that mines each of those coins. Don't flip flop around. Don't let someone else pick your coins. That's not what speculators do. They use their brain and make good decisions, and when the value of your coins go up, you did that... you win.
They're two separate things, really.
If you want to invest in certain coins, it makes more sense to mine the coin that is most profitable, and trade it for the coin in which you want to invest, than to mine the coin in which you want to invest directly (assuming the coin you want to invest is currently not the most profitable coin).
In this way, you not only get more of the coin you want to invest in, but you actually increase its value by buying it rather than mining it.
The downside is that it adds a step and has negative, "pump and dump" impact on the coins mined. Another way to do this, much more simply and without the negative impact, would be to just buy the coin you want to invest in.