Gambler

Rather than honing your skills, you rely on Lady Luck. Whether it's the addiction to the thrill, or your natural (mis)fortune, you are able to throw caution to the wind more freely than most. When you're on a winning streak you keep pushing it to make the most of your luck, and when you're on a losing streak your luck is bound to turn around at some point... Right?

Fortune's Favor

When you pick this archetype at 3rd level your luck naturally shields you from attacks that would otherwise hit, until it doesn't. You gain a bonus to your AC equal to half of your proficiency modifier (rounded up). If a creature scores a critical hit against you or you roll a critical failure on an attack roll, this bonus turns instead subtracts from your AC. This lasts until a creature rolls a critical failure on an attack roll against you, you score a critical hit on a creature, or the end of your next short or long rest.

Skills of the Addiction

Starting at 3rd level you gain proficiency in your choice of the following skills: Deception, Insight, Perception, or Sleight of Hand. You also gain proficiency with the Dice set or Playing Card set (Your choice).

Your proficiency bonus is doubled for any ability check you make that uses your choices.

Contagious Misfortune

By 9th level, your bad luck can bring down others as well. As a reaction to failing a saving throw you may choose a number of creatures equal to your proficiency modifier. Each creature of your choice has disadvantage on their next attack roll or saving throw within one minute. You may take this reaction even if failing the saving throw would cause an effect that prevents a reaction, such as being incapacitated or even death.

Once you use this feature you may not do so again until your next long rest.

Ace in the Sleeve

By 13th level, you know how to guarantee a win, as long as your opponent doesn't notice. Once per short or long rest when you take the attack action, instead of making an attack roll you may make a Dexterity (Sleight of Hand) check. If the check beats the target's passive perception score, the attack lands and you may use your Sneak Attack feature if it has not been used this turn. When you make a sneak attack this way, you may roll sneak attack damage twice and choose either total. The weapon used for this action must have the finesse and light properties. 

If a natural 20 is rolled for this check, it is treated as a critical hit.

Lucky Number

When you reach 17th level, you find a certain number seems to bring fortune along with it. Pick a number between 2 and 18. You gain the following benefits:

• If your number is rolled on a saving throw, you automatically pass and gain resistance to any damage related to this saving throw.
• If your number is rolled while you are effected by the negative effect of your Fortune's Favor, it reverts in into a bonus.
• When you roll your number on an attack roll, it is considered a critical hit.