Warden is a pretty good first character.
Generally you want to use a shield + spear, and the skill selection is very straightforward. Basically put points in whatever looks good to you at the moment, but be sure to finish the points in both masteries earlyish (mid-late 20's) so you get the most benefit from the health and stats.
Use
http://titancalc.com to preview your build, and remember you can always remove points from the mystic.
Some skills of note:
Gauge, Barbed Netting, Eviscerate, and Detonate don't deserve any points at any time. Bleeding is next to useless past the very beginning of normal.
Battle Awareness, Take Down, Rally, and Adrenaline don't usually need more than one point, as the benefits they give are less than what you can get elsewhere, although they are all pretty good. You want all of those for their synergies (except Take Down), which are awesome.
All four skills on the right side of the Defense tree plus Volley and maybe Wood Lore are probably what you want to max first (I find its a good idea to have at least one point in most of the good stuff before you start maxing skills), and Pulverize is the best of those.
You should put at least one point in Batter and Rend armor, as you have nothing else to put on your left click, and that gives you another multi-target shield attack (which does weapon damage + shield damage for alot of damage).
I don't recommend the marksmanship tree for a warden, as defense is blah without a shield.
For stats, you want to be able to have enough dex to use the best spears, and as much strength as you can get after that.