When you are saying in your balance -- are you meaning at a pool or in your GoldCoin Wallet?
As to your question on valid or invalid share means:
valid: means it is a share or "portion" of the block your miner worked and submitted before anyone else.
invalid: means your miner worked the share, but someone else had already submitted the work before you.
If you are mining on a CPU - you will likely want to look to see if it is actually worth the cost(electric, wear/tear on your machine, etc)
- I'm running 1.5 MH/S on my rig -- and, I'm only getting an average of about 2 coins per block found on the pool I'm mining at
Hope this helps.
