"Me gustas" means I like you.
When someone says "Te quiero" it can either mean, I want you, or I love you.
Usually, I tell my hubby, "Te quiero mucho" Which would then mean, I want you alot, but in spanish it is understood as I love you very much.
But if its sensual, and you say "Te quiero" It means I want you.
If you tell someone "Te quiero" They will understand that you love them..which obviously is deeper than just liking"
Lets say, your with someone, and you whisper in their ear "Te quiero" Then that can be taken as you want them in a physical way. Its all about attitude. Remember, its a romantic language.
If you just like someone, then you say "Me gustas" You would say this when youre getting to know someone, or dating.
If you like someone, dont say "Te quiero" Its like saying, "I love you" on the first date.