Magic: The Gathering Foundations is the best set for complete beginners
There's a very strong argument for Edgar Markov being the best Eminence Commander right now, and having played against him multiple times, he can be a real nuisance, but for now, it's still the Dragons that we fear the most
Cards that only work against specific colors like Devout Decree and Aether Gust might be tempting with their cheap costs and strong effects, but these are often just too narrow to be consistently effective
Ideally, you can start out early with cards like Siren Stormtamer and Fathom Fleet Captain, then cast your commander on the same turn you plan on fulfilling her end step trigger
9 Hexavus Too Many Counters To Count There are quite a few ways to get those pesky finality counters out of the way, and with Hexavus, you can spread the love a bit with two different abilities