Since you want a buffer with a pH near the lowest pKa, the sensible approach would be either (1) to combine 0.1 M citric acid with 0.1 M monobasic sodium citrate in whatever proportion results in a pH of 3.0, or (2) titrate a solution of citric acid with NaOH to bring the pH to 3.0.

It doesn't matter whether the citric acid is monohydrate or dihydrate (except insofar as you need to know the correct molecular weight) because you are going to dissolve it in water anyway.

If desired buffer pH is close to pKa1(i.e. 3.13) in such case weak acid is: citric acid(H3Cit) and sodium citrate monobasic (NaH2Cit)(as salt of conjugate base).

If desired buffer pH is close to pKa2(i.e. 4.72) in such case weak acid is: sodium citrate monobasic(NaH2Cit) and sodium citrate dibasic(Na2HCit) (as salt of conjugate base).

If desired buffer pH is close to pKa3(i.e. 6.4) in such case weak acid is: sodium citrate dibasic(Na2HCit) and trisodium citrate(Na3Cit)(as salt of conjugate base).

My query is most people use citric acid(Mol wt 210.1)(H3Cit) and trisodium citrate(mol wt 294.1)(Na3Cit) for preparing buffer at pH 3.0, In such case which pKa we have to use during Haselblach-Handerson equation for determining weights to be added? Theoretically we have to use sodium citrate monobasic (NaH2Cit)(as sodium salt of conjugate base) Mol wt : 214.11?

You may find these references useful.

https://www.sigmaaldrich.com/GB/en/technical-documents/protocol/protein-biology/protein-concentration-and-buffer-exchange/buffer-reference-center

http://staff.ustc.edu.cn/~liuyz/methods/buffer.htm

As pKa1 is pH 2.2-6.5 and pKa2 is pH 3.0-6.2 you will need to factor both in.

The use of the different hydration states of the sodium citrate comes down to cost and what the best value for money is from regional suppliers at the time. Depending on the purpose of your buffer you may also want to consider potassium citrate as sodium toxicity can be problematic for some media.