Well, for the first part...try NOT to triple post if your internet is lagging or slow.
To answer your question, play the game normally first. You don't know how long you will be playing to warrant buying in-game cash. As well, it is more satisfying when you achieved everything by yourself. If your in F2P, there isn't a huge demand on purchasing items. The most you will need to get is food and armour. If your P2P, you'll need money later on when your higher levels. But for the most part, if your playing normally (ie. training skills and CB), I don't see the need to purchase gold.
Runescape has a good aspect in which gold doesn't have too much affect on leveling. There are many different methods of leveling that uses tons of money or none at all.
To answer your question about RS money for Real money. Yes, it is real. However, similar to reality, watch out for scammers. I'm not familiar with the legit gold selling sites, so I cannot recommend any to you. As to how they transfer money to you, for the most part, who knows. They have 'secret' methods depending on your CB level, skills, and whether your F2P or P2P
