My trip to Sag A is pretty much the extent of my exploration and it was sufficient to get me straight to Ranger, I think. I got there and back in about 8 days of fairly intensive play, including a long weekend and the following Saturday. On the way out I alternated between 1000 Ly scanning and 1000 Ly hop-and-honk. On the way back I pretty much just hopped and honked as it was getting a bit monotonous by then.
You don't need anything that special gear wise, I got back with my hull integrity still in the low 90s and my AFMUs mostly full. Definitely get the absolute best scoop you can afford, it's a long way and you will be doing A LOT of scooping.
You might consider trying a diamondback instead, I've only messed about with the scout but the thing that struck me fairly quickly was that it seems to be made of asbestos, and can dive hard into the scoop zone and stay there without getting anywhere near the damage threshold, and I can even start charging the FSD from max scoop depth without danger. If the explorer is the same it might improve your quality of life a bit. Maybe someone who has used one can confirm if my impressions are correct.
If you want to get plenty of first discoveries, you'll want to get off the direct line between inhabited space and the core, so tack perpendicular to your intended course if you're seeing a lot of names on the system map.
If you want to boost your income take a detour to the neutron star fields as you approach the outer core, google can tell you where they are.
One other thing worth noting, that might have changed since I took my trip, is that the route planner starts to get VERY slow as you penetrate the outer core (so the last 5 kylies or so) due to the density of stars. You may have to switch to shorter legs - 100 Ly route calculations still seemed to be pretty trivial, but 1000 Ly in that area took my computer roughly a cup of tea and a cigarette to plot. YMMV as I assume this is CPU bound.
Make sure you take the time to stop and admire the view when you find some interesting objects, maybe make a log of interesting finds and take some screenshots. It does take a long time and it can get dispiriting when you look at the galaxy map and see how far is left to go so having something like that to look back on can help you keep going.