It will be very difficulty to find btc mining profitable at this stage, no matter you buy hardware now, make a pre-order on hardware or buy some cloud hashrate...
i found an hour of 180 gh/s for 8 usd.all calcs calculate in months not hours.So I dont know if this is profitable.(How fast does difficulty change? i know its every 2016 blocks but cudnt find more info)
what is the best pool?(according to chart: paypershare is best?)
Pay per share (PPS) is indeed not a pool, but a payment scheme.
PPS is best in terms of lowest variance, but the % fee is higher.
It may be better to use PPLNS or DGM (higher expected payment due to lower % fee).
FYR:
https://bitcointalk.org/index.php?topic=104664.msg1146110#msg1146110If you're renting, PPS is better though. You don't want variance when you are dealing with a set amount of time like an hour or a day.
Unless you are renting hashrate for just a day.
If you join a big pool like btcguild, the pool luck wouldn't vary that much with PPLNS.
For reference only: btcguild pool luck at this very moment.
Approximate Pool Luck* (24H / 3D / 1W / 2W / 1M): 92.069% / 101.504% / 98.734% / 102.433% / 101.802%
Though the average luck is at 98.7% for 1-week, you still get more btc using PPLNS than PPS.