The Yashica, like its contemporary the Rolleiflex TLR, functions best as a minimalist camera. You can get by on very few accessories, and instead concentrate on getting the best out of your compositions and the very high quality of your images.
To me the true joy of using a Yashica (or indeed any other TLR) for general shooting, is that you need so little beyond the basics to go out and produce truly good negatives or slides. It's a great feeling to set out on a 15 mile forest hike or mountain trek as I did last weekend, with your camera kit (I took my Rolleiflex T) and indulge yourself in shooting all day without the feeling that your bag is getting heavier with every kilometer (or mile) you walk.
You did not say which lens is on your D, the less expensive Yashikor (three elements,very similar to the Novar, Xenar or other 'budget' lenses) or the more upmarket Yashinon (four elements, very similar to the Tessar). Someone here will very likely chip in with opinions as to which is best, but take it from one who has used both, with care and concentrating on taking your shots at the sweet spots from f/8 to f/16, you wouldn't really notice any difference between the two.
Two items you will need right away are a reliable exposure meter and a lens hood. Some use the Sunny Sixteen Method (set the camera f/16 and the speed at the EI/ISO rating, so if you are shooting TMax 100 or 400 you would be exposing at 1/100 at f/16 or 1/500 at about halfway between f/11 and f/16. Adjust to open more (downwards, so from f/16 to f/11 to f/8 to f/5.6) to compensate for shade or less light. As an example, shots with TMax 100 in open shade in the forest would probably mean exposures of 1/25 at f/8 or 1/60 at f/11. Trying to explain all this further to you would be too complicated. Get a meter and learn to use it. You will never look back.
Accessories now. A UV filter, to protect your lens and provide a small degree of light ray protection. Later on you can add a few black-and-white filters if you plan to shoot 'monochrome', a yellow, maybe an orange, a green, and a red. Also close up lenses, which consist of two separate lenses, the actual close up which goes on the taking lens, and a parallel corrector lens to be put on the viewing lens.
If you find a good polariser at an affordable price, go for it. I bought one in the 1970s for my Rollei and while I use it t most one or two times a year,it serves its purpose,which is to cut or remove glare from surfaces such as water. Almost a must for good landscapes or seascapes.
The good news in all this is that any of the Rollei accessories (filters and close ups in the bayonet I), which can be a little expensive, but of assuredly very high quality.
A camera grip (generic brand will be fine) will provide that extra element of stability, as will a camera strap, ideally adjustable.The strap you can make yourself at home, with easily obtained materials.
You can buy a tripod later, if your photography involves lengthy timed exposures. The new carbon fiber models are a tad expensive, but very light. I recently bought one in Singapore, and I have to say I wish I had got it twenty years ago.
And film, of course. Bob's your uncle in this area, there is a virtually endless choice of good 120 emulsions. I use Kodak TMax for B&W and Ektar for color negatives, and on those nowadays very rare occasions when I shoot slides, any of the good Fuji brands. My camera bag currently has ten rolls of TMax 400 (the 100 is more fine-grained but with 120 roll film, the faster 400 is ideal for everyday use and you won't lose any quality or sharpness), two of Ektar, and three of Fuji Provia.
Roll film is ridiculously expensive in Australia where I live, and a roll will give you 12 shots, so this is where minimalist thinking again has its place. Compose your shots carefully. Aim for quality rather than quantity. One or two or at most three well composed images will satisfy you far more than machine-gunning 100 or 200 virtually similar images with THAT medium, as a brief foray in Flickr will quickly show you.
All the above rather stretches the meaning of 'minimalist' to an extent. Get the lens hood, the UV, the meter, and a grip or a camera cord, load your D with film, go out for the day, and shoot. You will be amazed at the results.
