There is nothing predictable when it comes to mining, take a look at our difficulty speculation thread and you will see that most things in mining happen out of order, however, with that being said, Sha258 is the most saturated algorithm, there are billions of dollars worth of gears that are already online and running, so it's physically impossible for difficulty to do 2x in a month, whereby with almost all other algorithms, a 2x jump in a very short period is doable.
The next thing to BTC would be anything LTC, although it's a lot less saturated and still has a huge potential to grow, it's the second best and far better than all other algos, with that said, I second NFW and Phill, if your power rate is not below 6 cents, forget it, in fact, if you backtest the past decade mining yields vs buying coins and holding, you would probably find that in 90% of cases those who bought the coin and did nothing ended up making more profit, you need to be very lucky to buy mining gears at the perfect time and be met with the perfect conditions to end up making some real profit otherwise -- it's a waste of time.
Not to long ago when the S19 was first sold, for 0.5
BTC, I dare anyone to say they made their ROI on that 0.5
BTC investment, there is no way on earth that an S19 made half a bitcoin after paying the power bill, go a little further, S17 went for like 0.4
BTC, probably only a few S17s on planet earth made as much up to today's date, it's all just psychological effects, mining gives you the illusion that you are somehow increasing your wealth, because you see incoming
BTC every day, it's a lot easier for your brain to mine than to hodl, but in the vast majority of cases, after a few years have passed, you will always regret not buying coins instead.
The above is based on my very long experience with mining, I have a very good power rate, probably better than 90% of miners, but looking back at how much
BTC I spent, had I just kept those
BTC I would have been freaking rich by now, however, with all the gears I run now -- I am just way too far from rich.