House Rule: Incremental Advance, adopted to D&D 5th edition from 13th Age

After a successful session, the DM can award the players an incremental advance. An incremental advance is always based on class specific advancement table for the next level in that class, with exception of Hit Points and race based advancements which are not listed in the table.

• Proficiency Bonus increment. 
• One feature listed in features column.
• Hit Points increment.
• Level based racial trait advancement such as Infernal Legacy granting ability to cast hellish rebuke at level 3. 
• Spell Slots increment.
• Spells Known increment.
• Cantrips Known increment.
• Rages increment (Barbarian).
• Rage Damage increment (Barbarian).
• Martial Arts increment (Monk).
• Ki Points increment (Monk).
• Unarmored Movement increment (Monk).
• Sneak Attack increment (Rogue). 
• Sorcery Points increment (Sorcerer).
• Slot Level increment (Warlock).
• Invocations Known increment (Warlock).
• Proficiencies Gained (Multiclassing).

A character gaining the first level in a new class via multiclassing is still restricted to the limitations listed above. For example, taking Spellcasting feature as incremental advance does not change Spells Known or grant the character more Spell Slots, these advances must be developed separately.