When I began the game, I created a PUG and got to about level 8 easy enough. As I started trying out other area's, I noticed enemies getting more difficult than I anticipated. In fact whatever strategies I tried, I found my self struggling.
One of my obvious problems was that I was still wearing crappy starter gear. The other problem I found was that I needed to improve my combat strategy by mixing in some new abilities.
To solve the gear problem, I discovered there were many guildleves that offered gear along with the gil reward. The catch here being that they were spread over each of the classes. What I did was attempt to only focus on those particular guildleves by juggling classes to be able to do each, which allowed me to get a decent mix of gear upgrades.
In fact, there was a guildleve for mining that not only got me an equipment reward, but during it I found a treasure chest that also contained more equipment. (On a side note I wonder if it would be wise to scout out the map to look for treasure instead of rushing to get the leve done quick, because on one leve I actually found two chest.)
To improve my combat strategy, I leveled several classes to level 6 so that I could play around with mixing different abilities with my PUG. I found that abilities like having Cure, or applying buff abilities like Stoneskin and Rampart before battle greatly improved my chances of survival. Imagine the possibilities as we get to higher levels.. can't wait!
I know I'm probably coming off as a pretty big noob and most of this is pretty obvious, but for those that are really struggling give it a try.
I would also like to mention that using macro's to changes classes and abilities on the fly, combined with using a controller made things easier and more fun too.