Fire, if only because those are the spells you'll be unlocking for the most part. They also have more area spells, which is good when you have enemies bunching up in PvE. As for a build? Um, take a mix of damage spells and possibly some defensive stuff. Inspiration line is popular as a secondary line, gives you access to more energy, a decent self-heal and damage reduction through stances.
I have found the fire to be the best as well, also later in the game most groups prefer a fire elementalist in PvE. Epinephrine had a lot of good points to take in consideration. Two skills I have found that are crucial to surviving are your energy storage skills and the inspiration (ether feast). The rest of your skills you should reserve for high damage fire spells that help go with how you play.
for noob people.. fire
coz its easy to use and doesnt waste too much energy .. depending on wat area skills so on.
then maybe later on when ur more experienced with how to use spells and when to use them .. maybe change to either earth or air... i personally like earth coz its very powerful and u can protect urself very well!!!