If you are not a professional developer like me, or not familiar with the Ardor platform, here are some quick tips you may find useful at the beginning :).
Difference between Ardor and Ignis
In short, Ardor is the parent chain, using the token ARDOR, which security the networks and package all child-chain transactions.You can’t do much thing only with Ardor chain.
Ignis is the first child-chain which has the most features , using the token IGNIS.
If you want build some dApps , you should focus on Ignis chain and may need some IGNIS coins.