Just keep in mind that while in theory, foil mythics and rares add to the expected value of the set, your odds of actually opening a valuable foil in any specific box is pretty low, since they are quite rare
It is more important to use it when it will be most impactful or when the effects will be immediately beneficial
Modern has fetchlands (lands like Flooded Strand that sacrifice to search up lands with a particular basic land type), which gives it some of the best mana fixing without the original Alpha dual lands
You can indicate you're using Mana from a specific Land by rotating that Land sideways, "tapping" it
These allow you to string spells together and drop your draw engine as early as possible
Overrun, Green Trample Sorcery A classic card, [c]Overrun[/c] is still famed for its ability to turn around a game even today