Start with a smaller aperture. There are lots of targets out there well within the reach of a small refractor or even a camera lens.
Unless you have loads of cash to spend on a sturdy computerised mount that will basically do most of the work for you, the way to go IMHO is to start with lightweight scope/lens + camera on a good mount (rated for several times the weight of what you're putting on it).
I am just starting out in AP myself after 10 or so years of watching others do it and learning about it along the way. I only have very modest equipment an old Japanese Polaris EQ (a modern Chinese EQ5 is comparable, but the EQ5 would probably beat my Polaris), a cheap but nice new camera and a couple of very cheap second hand lenses. But after just three nights I managed to capture 100+ galaxies, including some spiral arms at 60m ly, and many more closer-to-home DSOs.
Processing is where it's at and that's more time consuming and steeper learning curve than the actual data acquisition you do in the field (but there are things to learn there as well: tracking, alignment, focussing, image/photon quality-vs-quantity compromises).
My processing skills and software at my disposal are still severely lacking but here is what I managed: on my very
first night out and on the
second night out.
If you go for large aperture off-the-bat for deep sky imaging, you're looking at spending a lot of money on a good enough mount and you'll miss out on all there is to explore with a wider field scope/lens. An 8 or 10" will only let you image a tiny portion of the sky and tracking and alignment hassles will be much worse.
Planetary and deep sky imaging are very different beasts: pick one. If you decide to go for planets then a goto dob and a camera for capturing video through it should work well. But the same setup will not let you do anything exciting with deep sky.
Again, if you're loaded and want to do it all, this may not apply. Money will buy happiness (sort of): a large Cassegrain on a beefy expensive computerised GPS mount and the right accessories could do it all for you. IMHO though it's more fun to do it with more modest equipment, not in the least because then you'll be able to share your acquired knowledge and experience with many more people.
Not that I have anything against folks doing great things with large Cassegrains and fancy gear, but as a starting point, it'd be like buying a supercar to get your P-plates.