Welcome to the forums and the ever exciting world of budgie ownership!
You have certainly come to the right place as you will find all you need to know on budgie care here.
The information on the several articles and sticky threads at the top of each section of the forums will be extremely useful as you become more familiar with the species. Be sure to pay extra attention to the Diet and Nutrition as well as the Taming and Bonding sections of Talk Budgies.
I'm glad you have rescued and took in this lost budgie in need of help.
Even though you found it on a commercial area, it would still be good to try to locate the owners who may be worried and looking for their little friend.
You can do so by placing some flyers around the neighbourhood you have found him, including nearby pet stores/vets, you can also advertise online.
Contacting the local animal shelter would also be a good option.
From the photos you have posted it seems you have a budgie boy there.
In order to confirm gender, it would be best to take a couple of photos in natural lighting (no flash from camera).
What colour are his eyes? They look black to me and if that is the case, then you have a white based (blue series) dark-eyed clear budgie.
Given the fact you are very new to budgies and in order to avoid a potential overwhelming situation, it's best for you to take your time in getting more acquainted with the species and if you end up keeping this budgie, to work on forming a bond with him. This is easier to do so with a solo budgie.
The information on this link may be of use: https://talkbudgies.com/articles-gene...en-flocks.html
For now, there is no rush for you to get a second one and if later on you decide to get a friend for your budgie, you will have to get an additional cage for quarantine. https://talkbudgies.com/new-budgie-ar...necessary.html
Best of luck with everything!