I signed up for Medicare in June when I turned 65. I added Parts B&C and also I think it is Part D which covers dental and eye care/glasses.
My biggest takeaway is that it is going to cost some money to have anywhere near the kind of coverage that you may have had when employed and most of the costs were paid by your employer.
For example, the prescription drug coverage for a simple refill that used to cost me $10 when employed now costs $35. And my dentist, who is awesome and I have been going to for more than 20 years doesn't accept an HMO plan so it costs me about $60 a month for upgraded to a PPO dental coverage.
I looked into the so called "$0" coverage plans and they really only apply if you are at or near poverty level and want bare bones coverage that will cause sticker shock with the co-pays if you ever have to use it.
Figure on at least a couple hundred bucks a month for decent coverage, and possibly more.