how many cards can you have in hand mtg do multiple size-changing interact MTG? All 39 No Maximum Hand

If your deck is artifact-heavy, then Trading Post is a great choice since you can sacrifice the copy to return an artifact card from your graveyard to your hand, and if the copy happens to be an artifact creature, you can sacrifice it to draw a card, which will let you go up on cards from the transaction

This one was important not just for Commander, but Magic as a whole

Make sure the spot you choose is warm and dry

Any "as [this creature] enters the battlefield" or "[this creature] enters the battlefield with" abilities of the creature will also work

Quality and Feel I think this is the most important thing when you're deciding whether it's worth it to order proxies or not do they feel like real Magic cards