There are a few cards which have to be upgraded for a certain deck to operate properly. Example, Supernova in countless Speedbows, RoL in RoL/Hope.
Then, there are a few cards which will change upgraded. Chaos Power, Dissipation Field.
Knowing what to upgrade first will give significant advantage.
Anyway, hello there. Yes, come and look around and don't be shy to ask question! We will also be available at the chat.