Gotcha, I'm just really starting out with mining full time despite knowing about bit/altcoin for a while and I'm really just trying to throw stuff at a wall and see what sticks. I have a 2.5gh/s asic miner but it seems pretty worthless now that from what I've seen most sha256 coins have a huge difficulty rate and I'm not well versed on what kh/s mh/s etc mean.
Scrypt is a harder algo to mine, thus the hashrate is lower. A mh/s or megahash is 1/1000th the speed of 1 gh/s or gigahash. 1 Kh/s or kilohash is 1/1000th of a megahash. In other words 1000 kh/s equals 1 mh/s. 1000 mh/s equals 1 gh/s. Its like the metric system applied to hashing power. Since scrypt is harder to mine, it uses mh/s and kh/s. Bitcoin used to use them too up until last summer/fall when difficulty was a tiny fraction of what it is today.
Yes 2.5 ghs is worthless now, it will take well over a week to earn 0.001 BTC or about 58 cents. I imagine that you have something like a USB miner? if correct you should stay away from them in the future because they are always way overpriced almost never ROI anymore. You are probably paying more in power costs than you are earning already. SHA mining at this point requires a large investment to be worthwhile, as you spend more, you make more. They key thing you need to account for is power consumption.
For example Bitmain is one of the only truly trustworthy asic manufacturers. If you go to their site, you can buy a two Antminer S1's for 0.838 BTC for 360 GH/S, or about 0.00233 BTC per GH/S. But if you spend more money and buy the Antminer S2 you get 1000 GH/S for 3.961 BTC, or 0.003961 BTC per ghash. You may be thinking that the S1 is a better deal because it costs less per ghash, but your forgot about power consumption. The S1's use about 2 watts per ghs, while the S2 uses 1.1 watts per ghs, almost half as much. Taking this into account, the hashing numbers even out and the S2 is still a much better deal. Why? Power consumption is what makes a miner obsolete. The S1 will start start to cost more in electricity than it mines sooner, while the S2 will keep on hashing and earning a return.
That being said, I recommend you stay away from SHA unless you are ready to put some serious money into it and instead focus on scrypt. There are so many scrypt coins that the difficulty isn't as astronomical because you can just switch coins when difficulty jumps. Or use a multi pool like Waffle Pool, Trademybit or Clever Mining that automatically mines the most profitable coin and then automatically exchanges the mine alts and pays you in bitcoin. DO NOT BUY GPUs, instead because scrypt Asics are pricey you should consider a group buy from someone trustworthy like Waldohoover at CoiningSolutions. For $49 you get a 1 MH/S share in his current KNC Titan group buy. This would have cost over 10 to 15 times as much a couple months ago when you had to buy GPUs to build dedicated miners. There are also bitcoin group buys in the group buy section of bitcointalk, although they aren't as profitable or popular as they once were.
Mining is hard, its a hustle. You need to stay on top of it or else you will get burned badly. Do not invest more than you can afford to lose, especially since you are pretty late getting into it. Good Luck!
It may go down,but hope it will go up again. One thing which is a must is the stable network hashrate!
(you will find tons of hate in bitcointalk about darkcoin also)