Enough / not enough depends on girlfriend and her family. Not for us to answer. Set a budget and just go with it. For your budget that's what you're gonna get anyway. But then again, there are differences in colour, cut and clarity which can make a hell of of difference.

Certain group of people (stereotyping here, but mostly true) likes big and big alone. Don't care colour M or N, clarity S2 or S3 or even I1 or I2 and Cut being Fair also accept.

Others have preference for colour need to be at least E/F, clarity need to be VS and Cut need to be excellent.

In Malaysia, I suggest Wah Chan or Habib. Personally, I prefer Habib as their diamond stock is significantly more and for those in the know, you may be able to find bargains there. But for the uninitiated, both makes not much difference, Wah Chan may be a better choice due to them offering more ring choices.

When choosing Diamonds, those who tak tau just hentam tibai whatever the salesman bring you. Those who know a bit will want to see different diamonds variations of the 4Cs, usually different Carat for the same colour or different colour for the same carat. Those who knows slightly more will care about where the inclusion in the diamond is, how visible it is and can choose the best out of SI1 or VS2 or VS1. Those who know even more will care about the cut quality beyond Excellent, looking into angles and the diamond chart to get the best value out of the Excellent cut for the lowest price.

Colour is the easiest to tell out of the 3 (ignoring cut).