Can someone please explain to me what the various rewards for level Advancement mean or where I can get this information. Unless I missed something (quite possible), the rewards aren't described anywhere. Thanks.

Try original rules:

http://paizo.com/products/btpy8x6l

Short version:

Skill = bonus to your skill (+ 1 to you dice roll in a spesific test)

Power = one new power (aka new check mark to the lower part of your character sheet)

Card feat = new extra card to your deck (increase you deck size by spesific card type)

Card upgrade = you get a card that you can change to another card in your deck.

One very important thing. Every character uses a specific skill bonus when fighting, so a couple of point there at least for first thing! You'll find Melee/Ranged bonus for some, so look at the weapons they are using to stack correctly the bonus.

 

When they can fight and win then take a look to closing ability check to help them there if you have still free skill points.

 

Then, don't worry, I full rebuilt 2 characters in the first month when I got experience in the game. It's normal and you can easily collect gold and good cards doing that. GL mate