If you like to try a new type of working environment, the main Ubuntu with GNOME is a solid choice. GNOME is actually pretty great.

If you're more looking for familiarity coming from Windows, go with KDE and their Ubuntu-based distro, Neon - https://neon.kde.org -

Also, I have to mention, If what you want is the latest & greatest, want continual updates, great setup for multimedia & gaming etc. try https://manjaro.org - this is not based on Ubuntu, but rather on a distro called Arch, however the advantages are that you're always getting the latest software & as a result there's much better support in terms of the latest GPU drivers etc.

Many are afraid of occasional instability that can come with fresh software that Manjaro ships, which is something to consider, but it hasn't been a problem from what I've seen.

Always go with the most vanilla Ubuntu you can, since that will always have the most Google results when you hit an issue. Once you're confident, you can branch out from there.

Most recent version of Ubuntu.

There will be pain. You get the choice of horrendously outdated software where really annoying bugs don't get fixed for 2 years (if you go with LTS) and major upgrades that rarely go smoothly every 6 months (if you don't).

I'd recommend not going with LTS; one day you'll hit some missing feature in GIMP, Inkscape or whatever you're using and start cursing your life choices.

If you are disciplined enough to document the changes you make to the system (installed packages, changed settings, anything outside your home dir basically) you can simplify your life a lot, because you can reinstall from scratch easily. While the update process has gotten better, old wisdom often suggested to reinstall instead of attempting an in-place upgrade.

If you want to try Ubuntu, try the latest long time support release (currently 18.04).

All Ubuntu (and indeed most major Linux disto) releases come with a "live image" - so there's no reason to start off with an actual install - it's easy to boot off an USB and play around.

In addition to the other replies, it also depends on your computer. I have a new Matebook 13 and 18.04 didn't quite work as well out of the box for me as 18.10, because it lacked some of the newest drivers and the laptop has some pretty new components. But if you have an older laptop, or a desktop computer it's probably less relevant so the LTS version is likely better.