The choice of the angular range depends on your compound and also on the configuration of your instrument. For inorganic materials we do not expect diffraction peaks at low angle, so in general it is sufficient to start from 10°. If you have an organic material, suc as a drug, it could have diffraction peaks at lower angle, so we can start at about 5° or lower. You can start near zero to analyse thin films, working with the grazing angle mode.

At 2T angles range less than 10deg you will see some broad peak/peaks which is corresponds to small angle scattering from non crystalline materials like glasses, polymers, films, oils/waxes (especially with silicone), etc... (coming from materials which are used as a sample holder or for preparation. also the ground noise is strong there and rise more strong at 2T=>0, because atmospheric gases also scatters the power of primary beam.) This is because any materials which is consist of molecules /atoms interacts with and scatter x-ray radiations.

Your data would slso be impacted by the x-ray itself if close to zero angle, i.e. below 5deg [2theta].

We cannot measure the XRD pattern below from 0°, this is important to keep the detector from getting burned as the X ray falls on it. A goniometer is like a high-tech sample holder; it serves to hold the crystal in the beam of X-rays, but it also rotates the sample to precise degrees. When 2T is zero, the beam of X-rays not falls to the sample but to the detector causing a damage.