Welcome to the forums!
Can you be more specific in terms of explaining the methods you have used so far in trying to tame your budgie?
First and foremost, it's important to work on establishing the foundations of trust and this is done by sitting close to the cage and by talking to your budgie in a calm, positive, encouraging and reassuring way.
By doing so, in time your budgie will get used to your presence and realize you are not threat and with the help of your voice, you will be able to make the first connection with your budgie.
When you notice real signs of receptiveness and curiosity from your budgie, that's when you can progress in terms of training. If your budgie doesn't like millet, you can offer him a few loose seed and see if he approaches your hand for snack time.
Also if your budgie is currently on a mainly seed diet, giving up on offering him fresh foods is not the way to go, just like with taming, we have to be persistent and consistent. You can present veggies in different ways, sprinkle a few seeds to to entice him to try it out. Some budgies like big leafy greens attached onto the cage's bars, they would even at times bathes on a dripping wet leaf and proceed to eat it too.
Others prefer to eat chopped up veggies placed on a bowl. Romaine lettuce is good starter veggie for a more stubborn budgie.
For all the detailed information and tips on improving your budgie's diet, be sure to check the sticky threads at the top of the Diet and Nutrition section of Talk Budgies.
You can also make use of the information found on the stickies here at the Taming and Bonding section and in time, depending on how your budgie responds to your training approach and by closely watching his behaviour, you will be in a better position to determine if getting him a same species friend is the best decision for his overall welfare and happiness.