Illinois (Updated January 17, 2020)

Harrah's Joliet has three video poker variants worth looking at, though none are great.

9-6 Double Double Bonus Poker, $1/$2/$5 per credit, as well as $5/$10/$25 per credit, 1-play (98.98% return). If you don't have the patience to play the $1 progressive below, you can play at higher denominations and get this done faster. There are $1/$2/$5 slant top machines near the bar, and more $1/$2/$5 in Game King and Superstar Poker bartops. The high limit area also has $5/$10/$25 machines like this (slant tops). There's a few $1 machines located two rows from the bar, but if you're going to play $1, you might as well do the progressive (see below).
Average loss getting to Diamond: $510
Average loss getting to Seven Stars: $5100

9-6 Double Double Bonus Poker, $1/credit, 1-play with progressive (98.98% return or MORE). This is a "progressive" machine. These are new "Game King" machines located outside video poker alcove near left hand side of the bar. To figure out the actual return, look for the royal flush payout for max credits. For every $20 over $4000, add 0.01% to the return. Then look at 4 aces with any 2/3/4. For every $16 over $2000, add 0.01% again. Sadly, this only a 1-play, $1 machine, so it will still take you 10 hours to earn 2500 tier credits.
Average loss getting to Diamond: $510 (less with progressive as described above)
Average loss getting to Seven Stars: $5100 (less with progressive as described above)

Double Bonus Poker: $1/credit, 3 play (99.11% return). Located outside the video poker alcove. This will earn tier credits faster due to the 3-play. Note that this is Double Bonus Poker, not Double Double Bonus. The paytable is 9 for a full house, 7 for a flush, 5 for a straight, quads at 50/80/160, and 50 for a straight flush. Verify these payouts before playing. You will find these on the "Triple Play" machines right outside the video poker alcove.
Average loss getting to Diamond: $445
Average loss getting to Seven Stars: $4450