The 4 basic C's of a diamond are Color, Clarity, Carat and Cut.
In uncut/ semi-cut/ rose-cut diamond jewelry, the most important attribute that you must pay attention to, is its color. The whiter (or more colorless) the diamond, the more expensive it will be.When you choose the diamonds for your Polki jewelry, make sure that the diamond does not look too white otherwise it starts looking like glass or fake which completely takes it off from the design. Also if the diamond is very bright, it will over power the pattern very easily and take you away from the 'old jewelry' look. This does not mean that the diamond should be completely dark in color, but choose colors which will compliment the design as well.The one thing you should try to keep steady through the design is the base color of your not-so-white diamonds. This means that stick to various shades of either yellow or brown in one jewel rather than mixing some of yellow and some of browns in one product.Matching the smaller diamonds with the larger ones is slightly tricky since the color of the stone can vary a lot based on the way they have been set.As a general rule, it is best to get a finished product and get a feel of the overall product rather than try for the best of whites in rose cut diamond jewelry.
This is an important factor which exponentially increases the price of a diamond. The diamonds used in Polki need not be the best in the clarity grade, but try to get the stones which have lesser faults on the table. Choose a median between the cost of the diamond and its look. For the smaller diamonds, I would suggest that you go for SI and below because with the setting , size and color, the clarity will really not matter all that much. Concentrate your budget on the bigger diamond which will show the faults fairly well.
The bigger the diamond, the greater is the per carat value. This is true for rose cut or uncut diamonds as much as it is for round brilliant cut diamonds.
Even though in Polki jewelry, the design pretty much dictates the size of the diamond, you can make a smaller diamond look bigger with simple techniques.
Use several very tiny diamonds around the bigger one.
Use white rhodium around the diamond setting and immediately surrounding that use a line of enamel or colored stones.Use contrasting colored stones around the diamond in very small sizes as compared with the main diamond.
You can use 4 or more diamonds instead of 1 big one to cover the same area in a design.
This is the one aspect of a rose cut diamond which cannot be assessed very easily. The cut completely depends upon the design and the budget. You can sometimes save money in Polki jewelry by using shallow cut diamonds as compared to deep cut ones. Use well cut rose-cut diamonds for the smaller stones which would give your product a neat and clean finish. Since symmetry of the stone does not matter, you can play around with the stones and create a mosaic network of diamonds to best suit your design needs.
Remember that a deep cut diamond will look smaller when set, weigh more than shallow cut diamonds of a similar visual size, and it may look much darker because of internal reflection hence taking us away from the color of the diamonds used in that jewel.