Join Date: Jun 2015
Location: Atlanta GA, USA
Wow what a nice scape for a first tank! Don't beat yourself up, you are on the right track. The store advised you well, that's definitely a good sign.
Just an FYI in case you didn't know, but plants are fine in a non cycled tank, in fact, they will help cycle.
I would buy a live bacteria product, such as Tetra Safe Start, and it will cycle your tank instantly by adding the necessary bacteria, and you can keep the endler.
At the moment, you don't want to do water changes, but once established I'd suggest 20-30% (~1 gallon) every week or two.
As to Ferts, you can see how they do without supplementation, and if it looks like they need supplementation Seachem flourish is perfect for low tech tanks. You really don't want fast growth in a tank that size, otherwise you'll be trimming every week!
Purigen is nice to have, but not neccesary.