Typically, Modern decks run between 18 to 23 lands, depending on whether they're blue-based, aggressive, or midrange/control decks
Pair either one with your commander or any evasive creature, and youll be drawing cards for days
Try one of these infinite card draw combos that can be easily started and stopped so that you can drain each of your opponents life totals without completely milling yourself out: Lichs Mastery: A great one-card combo with Queza that gives you infinite draw, triggers, lifegain, and more than enough life-loss., Drogskol Reaver also does this, which gives you some redundancy
Take the Mountain as an example
It's also pricey on the secondary market since it's so powerful and dominating at around $20 here at CoolStuffInc.com but it's worth it