To add on to FaeryBee's point about adding another budgie-
My budgie, Niko, was a solo budgie for the first year of his life. He was happy even though he never truly bonded with me. However, when someone found my second budgie wandering around outside, I couldn't say no to taking her in and eventually keeping her as an owner was never found. Fortunately, they get along okay and don't need to be housed separately, but they are definitely not best friends. You always have to be prepared for the possibility that they won't get along and will need to be housed separately.
~Niko and Tetra~