It depends upon the application. But for cheap and High strength, I'll suggest Maraging Steel or Stainless Steel 316L.

But one thing I must tell you that Selective Laser Sintering method has now become an  obsolete technology. Better you look at Selective Laser Melting or EBM method.

The best material is the one that best fits your requirements without being over-engineered. I worked with laser tecnologies before applied to a titanium powder, and results were not good. The problem with lasers and target material, is the reflectivity of the later resulting in poor particle-to-particle bonding, this added to the fact that final components were distorted geometrically. Nowadays, As Amit mentioned, EBM is the best (Arcam's), and although at the very beginning they only processed Ti6-4 ELI, the catalogue of materials to process is growing.

Hi Hugo,

Your view on the Titanium with regards to laser is right but we are working with Ti powders in Selective Laser Melting Process and we've successfully achieved to minimum criterion required by Aerospace Industries and standards. The surface integrity, Strength, Ductility, Hardness, etc. have been achieved by certain in house parameters that we have developed.  

I've not worked in EBM 3D Printing, so I cannot comment on that. 

Thanks for your answers guys :)

I also need some assistance regarding Process control. Can anyone help it out ? or give some related contacts ?

Steel or Aluminum alloys

titanium alloys

it will depend on your application and I would recommend also checking your facility equipment if you can store and handle it safely and if you can ensure that the material will not degrade. Some powders are more sensitive to open atmosphere, moisture, etc and can degrade easily.