Welcome to the Forum.
Please check the rules if you haven't checked them out yet! ^_^
If you've just started out, you should have 3 tradeable Time Elixiers, which you should keep yourself, since they are the in-game currency you could say. Save them up and grind in Events for Units/Time Elixier/Potions. Potions are also a currecny in-game, but Time Elixiers are more valued, since they've more use for people. Time Elixier skips your cooldown on Quests and it is very useful in Event that required TE.
Potions skips the cooldown for the training.
Apparently, it should be easy for you to get several 5*s, thanks to the 7*s.
I'm going to link you some useful guides:
GUIDE: Getting Started in Fantasica (without spending money)
WALKTHROUGH - Free Player
The Beginners [ GUIDE ] to Trading
Please check these links out. These are very useful Guides and may answer your all up coming questions.
Also, if you've any more questions to ask, don't hestiate to ask, if it's about Fantasica, the sub-forum "Game Discussion" shall be the place for asking question, for anything non Fantasica related, the sub-forum "General Chat" is the place. Otherwise, the guide section has a lot of informations, also links to several Unit/Monster/Arena spreadsheets and etc.