Nice post Scythe.One thing worth remembering regarding ftlb's.As a general rule of thumb spring guns prefer lighter pellets and pre charged prefer heavier.
This is in no way set in stone as skirt thickness/hardness/the rifling all play a part,including pellet weight.Just because your particular gun is shooting close to the limit with a particular pellet doesn't necessarily mean that it is 100% legal.
The police (if you were ever unfortunate enough to have them test your gun) can test it with whatever pellet they choose. The safest thing is to have your rifle chronographed with as many pellets as you can find,you should try as many different ones as you can anyway to see which one suits the gun you're using .
My HW80 is set so .177 RWS Superdomes leave the rifle at an average 10.7 ftlb's,still perfectly adequate for all british air rifle quarry but it gives me some leeway if the rifle was ever tested with something like RWS Hobby or one of the new composite style pellets.
If the gun goes over 12ftlb's by even a fraction you could very well go down for it (at the very least they would likely confiscate and destroy it).
For a first time gun I would personally recommend a springer.They're self contained and are much easier for first time tinkerers who want to venture into tuning their gun.They're also more unforgiving of poor technique and generally are more accurate with a relaxed hold.
If a scope is going to be used a spring gun really needs a quality scope and preferably a good one piece mount.Spring rifles have a push/pull recoil due the piston first travelling at speed then coming to an abrupt (though cushioned) stop,and can wreck a cheap scope pretty fast.
Definitely better to start with open sights though.
.177 vs .22 is a never ending debate,both will do the job if the shooter does their part.I prefer .177 at 12ftlb's for it's flatter trajectory.
Gun oil is great for protecting the bluing,but for the cocking linkages or the barrel hinge i use a molybdenum grease.
The most important thing in this climate though is make sure the gun is on the right side of the limit.A chrony is money well spent,but it is vital if you want to start down the path of home tuning (and who doesn't)