Diamonds 4C are weight, cut, color and clarity.
If you want a diamond ring with more carats, you must first choose a larger diamond weight as much as possible within the budget.
Secondly, choose cutting. I suggest you choose 3EX perfect grade.
Then choose the diamond color, D color is the best and Z color is the worst. You can appropriately reduce the color of diamonds within the budget and choose between D-J colors.
Finally, choose diamond clarity, there are several grades, from high to low: FL, IF, VVS, VS, SI, P. I suggest you choose between FL and VS grades, and the budget is low, which can be reduced to SI 1 grade.