Welcome "Over Flanders Fields", Redmonkey!
Flying the Entente is the harder part in OFF, as you have to cross the lines, which the German scouts rarely did.
The advantage of flying on your own side of the lines is the warning you receive by Flak/Archie.
The grey puffs of Archie or the black puffs of Flak would assign enemy aircraft in your area, long before your naked eye could see them.
You loose this big help once you cross the lines.
And not only that - Flak/Archie will now fire at you, and even if they don't shoot too well, the enemy scouts will get pointed out, where you are.
Flying the British side is the toughest in OFF.
You will never be in the rather quiet areas. Your headquarters are mostly planning and fighting offensively.
You will mostly have to cross the lines; day after day; week after week; month for month.
In April 1917, the average life expectancy for new British pilots was 17 hours.
That being said, a British campaign for a beginner would better be early on - best before the Albatros fighter appeared.
Scouts like the Bristol Scout or the AIRCO DH-2 can hold their own against Fokker E.III.
But the Albatros brings back all advantage to the German side.
Easy to fly early aircraft IMHO are the Bristol Scout, the Nieuport 11, the FE2b, and - excellent scout - the Sopwith Pup.
Then came the Sopwith Triplane, mostly for the boys from RNAS, and it was a dangerous, fast and manoeuverable fighter.
But they are all lacking firepower, cause the Germans had from the Albatros D.I and D.II on twin 08/15 LMG.
Devastating, when your craft gets hit.
Personally, I would probably grab me Arthur Gould Lee's wonderful book "No Parachute!", and join his squadron at La Gorgue.
But if you want to last in a campaign, my best advice will probably not be to your likes - it is:
Don't go for kills, not for victories piling - save your valuable life first. Always.
Fly it as if you could get hurt, as if you could bleed to death, or as if your only choice after having been carefree might be,
wether to fall or to burn to death.
The more humble you act, the more do you honour the real flyers, cause you won't be showing up.
Cause you won't have ten times more victories than they ever had.
You could feel like being one of them.
Make it your first aim to last longer than 17 hours.
I'm sure RAF_Louvert, Dej or another British flyer can help you much better with details and good advice about flying in the RFC.
I wish you good luck. If you only enjoy OFF half as much as I still do, you're in for a wonderful time.
.