It depends on which mods you want. Gambling is -5/+4 of your character level. If you need the 2-3 dex mod (alvl 13 mod) use a level 18 character, and then every item you gamble has a chance for this...
You could also consider using max/-req jewels in a 4 sock armor. Even ancient armor only requires 40 str if it has 4 -req jewels. If my math is correct, using 3 max/-req jewels and one plain maxer s...