After some consideration I think I’ll try to go with this bet

100 on A

100 on C

100 on F

100 on G

100 on I

250 on red

250 on odd

If my math’s correct this spends 600 on one 48.6% chance to win one column for 1200 total winnings, 1100 win + 100 back. Spending another 200 each on two more 48.6% chances in red and odd each possibly paying back 400. In my column picks there’s 12/18 reds and 10/18 odd so IF I get a column win I also stand a decent chance to trigger one of the red or odd wins which then will boost the payout to 1600 or 2000. So it’s not a high winning strategy but I think it stands a reasonably chance of getting something.

Of course my bets are not hedged here. I’m betting against the house advantage with my best possibly chance of getting anything being 48.6%. Even betting both red and black you’re still not sure to win and you’re just going to come out even if you do. I found in my tinkering with the numbers that the game is very well balanced for any combination of picks but of course always in house favour.

Edit: Changed my bet to comply with the 7 bets rule by removing the bet for column L and spread the 100 to make red and odd 250 each. This has slightly lowered my chances of winning but increased the potential maximum payout.