Can anyone suggest some bonus offers that I should apply for and/or what I can do to better maximize returns?

Credit was previously not that great and is now 700 or so on average. My application pattern has been taking whatever card I could get (when credit was really bad) to applying for the credit card of whatever program I had points/miles in. Currently have:

American Express
Gold Delta SkyMiles - 50,000 miles bonues received
TrueEarnings Card from Costco - No bonus, used whenever I'm at Costco

Barclays
Hawaiian Airlines Bank of Hawaii World Elite MasterCard - 35,000 miles bonues received
This is also my main card for spending

CapitalOne
Quicksilver Visa - No bonus, from back when I badly needed credit
QuicksilverOne Mastercard - No bonus, from back when I badly needed credit

Chase
IHG World MasterCard - 80,000 point bonues received
Marriott Premier Signature Visa - 70,000 point bonues received
Ritz-Carlton Signature Visa - 70,000 point bonues received
I actually stay at Marriotts a lot. It's my preferred hotel for travel

GE Capital
Old Navy Card - No bonus, from back when I badly needed credit
TJ Maxx MasterCard - No bonus, from back when I badly needed credit

JCB
Marukai Premium JCB - I've always thought it would be so cool to have a JCB, works great at the supermarket too

Local credit union
Visa - No bonus, from back when I badly needed credit