As a zero mana spell that is instant you can do a lot of things your opponent wasn't accounting for, perhaps it is just for fixing, they assumed you couldn't play a Cryptic Command due to lack of triple blue but the Search sorts it out etc
With infinite mana, well - I guess thats that
This year's cards have already been released at some locations in Germany
For example, Blue/Green is an archetype that revolves around scrying, so you will want to prioritize cards with that ability
Higher because it has a strong creature base that synergizes well, but not the best since it has a lot of early creatures that just dont synergize with the theme
The number of support cards is here for exactly that reason, as it will be better to use the cards you have wisely rather than have many to choose from