[SteamWolf]

250cc is an ideal first bike and you will be teriffied for the first week, comfortable in the third week and bored with it in 3 months. Plan on stepping up to a 600cc in 12 months time. Don't go straight to a litre bike or you will die. The reason is not so much riding beyond skill, but learning what levels are needed. Perception is VERY different on a bike than a car, and it's very easy to have an un-co moment with throttle, clutch and brake. On a 250, this leads to a stall. On a litre bike this results in a huge wheelie with your face dragged along the ground until it flips and lands on you.

Always look where you WANT to go, don't look at where you DON'T want to go, because the bike follows your eyes (target fixation).

Always assume everyone else on the road is an imbecile and is actively trying to kill you.

Don't buy a Harley (or other cruiser type bikes). They are ****. Unless of course you like freeways and straight lines, in which case they are awesome. But then so are convertibles.

Take a rider training course of some sort. Not only are they awesome fun, they give you a massive head start by teaching you tricks and tips that otherwise take years and gravel rashes to figure out. There's nothing wussy about a bit of training.

Buy a good helmet, good gloves, good pants and good boots. The jacket is surprisingly less important, as long as it's got decent padding. The sorts of crashes road bike riders experience are usually more impact compared to race riders that fall off and go for epically long slides.

Royal Enfield is a poor quality bike but a cheap way into that classic style. Buy the Triumph! Enfield is a 50's design made in India with 40's equipment and 50's tooling.
Triumph is a modern bike made to look like the classic style, and will be very reliable, and handle well.