Got it. What are your common buckets of spending? Travel, restaurants, gas, groceries? That will also help advise.
For starters, I'd recommend you look into the following programs:
Chase Ultimate Rewards - redeemable for United
American Express Membership Rewards - redeemable for British Airways (AA) and El Al
Chase has several cards with big sign-up bonuses: Chase Sapphire Preferred (2 points per $ on travel and restaurants), Chase Ink Plus/Bold (office supplies).
Amex MR has several cards as well.
You may want to either focus on one program (Chase UR) or diversify. Look around the forum for ideas.