Lots of good advice. A lot of people don't realize how wifi and mobile data users differ.
But this is a bad idea, more and more:
Redirects – install a simple script on your site that will redirect users to a partner
Search engines punish for it and leaves users with a bad taste in their mouths as they get redirected away from what they intended to see. Affects your productivity, too. Be upfront and when mobile is detected, warn users that site is not intended for mobile and offer an alternative if you must go that route. Via banner or whatnot as you mentioned but leave the user the opportunity to STAY on the initial page. Redirecting is a waste of traffic. You never know, that phone-wielding user might also have a tablet or laptop that'll use your site fine.. and have credit cards waiting to be used.