Not sure if you will be able to get anything better for that price... Ideally the internal width is between 20-25mm but 19mm is absolutely fine as well. If 80% of your riding is done on road 700C is a good choice, I wouldn't go for 650B in your case.
There are multiple tire possibilities but a good bet would be to get a 30mm Schwalbe G-ONE or Panaracer Gravelking 32mm. Set them up tubeless and use 40psi offroad and 60-70psi on road. If your off roads are a bit rough you could consider going for their 38mm versions as well, they still roll very well on road in those wider sizes with higer psi.
You could always go for this wheelset with 30mm tires now, and buy another 650B wheelset + 47mm tires for offroad rides at a later stage.
Thank you very much for your response. I am going for a 700C. According to the website, I can fit in up too 700Cx42. For the tires, it is within the budget. Would a 30mm give much comfort and roll? I use my bike for everyday commute to work and weekend rides.
I am also looking at the Fulcrum Racing 5. Around $375. But I don't think this is good for a gravel ride.
I don't think I will be able to afford the extra 650BX47 set in the future.
Where is here?
What size tire do you want?
Local Bike Shop near me. Preferrably 700Cx??mm. Any size that would be comfortable and have a good roll.