I can't advise much on long lens as I shoot wide mf on my leica.
But I can say after going through loads of tripods and heads, don't skimp on the pod. Get a carbon with a decent head. Carrying it on long expositions and getting thrown in out cars etc you need something decent. Main thing is the build quality and weight over high imo. You can aways find ways of getting higher and sometimes makes you more creative.
Never had a monopod, but if you already have a tripod then it makes sense to get mono. If you have neither get a tripod as it opens up so many more opportunities like night photography, studio style shots etc.
I have had many budget pods from loads of brands. The one I've been using for past 5 years is a velbron geo n640. With a gitzo head. Probably around £550 in total. But it's light reliable and already had 5 years service without an issue. Get a pod that can also stand low to the ground, again this will offer a totally different perspective and open up some of your creativity. Great for water reflection shots.
Good luck