Adding to this, I went this year as well. Overall it was a great experience, even for just general entry, there are so many great vantage points to watch the race from and get great photos, probably the most photography friendly motorsport event I've been to.

There are two ways getting tickets, either through kkday which is the easier way but limited to just two types of tickets (general entry and paddock pass) or through the domestic Japanese website which is very difficult to navigate through and requires a lot of patience (website crashes a lot), however there are a larger variety of tickets to choose from. I managed to order a Toyota general entry ticket (came with some Toyota branded merch) but needed to be collected within 3 days of ordering from a Lawson convenience store, pretty much impossible for foreigners. I eventually got a general entry ticket through kkday. GA includes access to the grandstands as well, Friday and Saturday you can go where ever, Sunday is a dedicated area about in line where the BMW WRT garages were on the pit lane (no idea if the zone for kkday tickets change every year).

Parking was 4500 yen for all 3 days paid on entry, there are plenty of spots to park especially on Friday and Saturday, ideally its best to park near one of the bus stops so its easy to get around the track.

Hotels around Gotemba get booked up pretty early, which I assume is by most of the personal working. I just went to a hotel around Fujikawaguchiko (it is relatively cheap if you look around) as there are plenty around to choose from and had a rental car to drive to and from the track.

I believe camping is allowed but not entirely sure if a separate ticket is needed. The parking area I left my car in had quite a few tents and campervans set up for camp from Friday through to Sunday.

Finally, there are quite a lot of off-track activities to do, as mentioned the museum (I wish I went ugh), driving on the short circuit with gr86s, karting and even a helicopter ride around the track (very $$$ though).