Nice attempt Klaussius. Here is the original stacked tiff if anyone wants to have a go at it.
When I started AP I used the 100ED with reducer, giving me 750mm f/7.5 on a full frame camera. It is kinda slow, but easy gradient wise. I only started using widefield when I already had mono, narrowband and the like. Maybe I am spoiled and give up too fast
Now this picture below is also widefield (105mm) but with narrowband h-alpha. There were zero gradients in de stacked tiff. Processing was easy and very rewarding:
20200707 NGC700 Ha 105mm.jpg
Getting back on topic for a beginner: maybe it is just a matter of choosing a path. Look at what appeals to you. Widefield can be very tempting if done right, and if you have nice dark skies it can be even more rewarding.
Not meaning to hijack the thread, but here's my result with a bit more effort (not too much though) based on your linear stack:
After finishing, I realized that maybe I stretched it too much. It's noticeably flatter. I could have dialed down on the HDR stretch to retain some dynamic range. Also, there was a lot of walking noise that's very hard to deal with, and I think I can see some CA that's kinda bothersome and is begging to be fixed. But I'd say the gradients are under control, although not totally gone. That's about the best I can do without manual touchups.
I think this is relevant to the thread. Gradients are perhaps the bane of beginners, myself included, and it takes some experience and patience until you get to a point where you know how to attack them. They should not be feared, but it is true that wider fields suffer from more pervasive gradients. At the same time, wider fields have smaller features, making gradient reduction actually easier. The hardest gradient to remove is that which has the same feature scale as your target. At 750mm FL, your target may very well encompass the whole shot, and removing gradients under those conditions without nuking the target itself is hard. At 50mm, there's no such thing, so you can go nuts on ABR without remorse.
Shorter FL are thus only hard on beginners because they haven't learned how to approach gradients yet. But that's good. Short FL imaging is easier in other respects, like tracking, so you can focus on learning how to deal with gradients, calibration and all the other problems.
And yes. Narrowband, especially H-alpha, is amazing. It's pleasant to work with, because the data tends to be so much cleaner. Gradients are there, but a mere fraction of what they are in broadband, and you get much better SNR from the start as well. But narrowband imaging requires longer exposures, and beginners may have a hard time getting consistent tracking to expose for 5-10 minutes per sub. I've recommended H-alpha imaging to beginners, with the caveat that they should get their guiding straight before attempting it.
I will admit that the f/4 scope suggestions are rare, however I feel like I've probably seen a f/4-ish (maybe with reducer) refractor being suggested before. Or at least in theory you could depending on things. I think the Stellarvue SVX70 reduces down to like f/4.8 so not super far off of f/4, maybe about 1/2 an exposure stop photographically speaking. Granted I don't know if I'd call that scope beginner friendly due to the price tag...
Either way I don't think anyone will (or can) argue that f/4 is going to be faster than f/6 which can definitely help just ease the exposure times down and help the guiding requirements. The bigger thing is really the overall exposure time though, so whether your subs are 2min or 5min if you expose for 15min the results are going to be fairly similar.
F4 may be tricky, but F5 isn't. I was merely starting, although I had some experience with a 70mm achromat, when I upgraded to an F5 150/750 newt that I still use today. It was an automatic step-up. Sure, tracking was less forgiving, but optically I had few issues. Zero at first. Collimation was only a problem when I forgot to check it and, luckily, the scope arrived in good collimation so I didn't have to worry about it at first. Still, the first time I tried to collimate, it was a breeze. It was done in under a minute, and wasn't particularly hard. It just takes a bit of reading to know what not to do (like not messing with the secondary unless absolutely necessary) and how to use the tools.
I'd say an F5 is a good starter scope.