Modified Basic D20 rules for D&D5e

>Limit max skill ranks at 2 for 1st level, 3 for 5th, 4 for 9th, 5 for 13th, and 6 for 17th, like proficiency bonuses. Skill ranks cost 2 PP to advance instead of 1. This excludes Profession (class), Toughness, and Fight/Shoot for the sake of martial class feats (but attack bonuses are limited like normal skills).

>If you take the Expertise bard/rogue feature, skill rank maximums are now doubled for 2 broad skills of your choice. At character level 10, choose another 2 broad skills to double the maximum skill rank. The skills you choose now cost 1 PP to advance.

>The "reward for showing up" is now 2 PP instead of 1.

>Spell Save DC is treated as such: 8 + spellcasting ability + spell level

>The Spell Penetration combat stat is now used instead of spell attack, it is treated as such: current max skill rank for your level (2, 3, 4, 5, or 6) + spellcasting ability modifier

>Backgrounds offer no bonus proficiencies, skill ranks, or feats. You have the option to buy your optional background feat, and still gain the starting items for free.

>Racial bonuses cost nothing and are automatically applied to your character. Racial skill proficiencies are treated as free Skill Focus feats (applying a +3 bonus to a specialty)

>Spellcasting
You gain spell levels and slots as you progress with buying the spellcasting powers (Wizardly Spellcasting, Druid Spellcasting, etc.) as if you were leveling up a normal 5e spellcaster i.e. gaining slots and spells. However you can only buy a spellcaster level up to the Profession (spellcasting class) skill rank you have. For example if Johan has 1 rank in Profession (Bard) and 2 in Profession (Sorcerer), he can take Bardic Spellcasting one time and Sorcerer Spellcasting two times. Thus he will gain the known spells for a bard at 1st level and the known spells for a sorcerer at 2nd level.
The spell slots in which you are able to cast work just like multiclassing spellcaster classes. The earlier mentioned Johan being 3rd level and putting ranks into Bardic Spellcasting and Sorcerer Spellcasting will have four 1st level and two 2nd level spell slots.

-Skill Specialties-

Athletics
(Acrobatics)
(Athletics)

Awareness
(Insight)
(Investigation)
(Perception)

Interaction
(Deception)
(Intimidation)
(Persuasion)

Knowledge
(History)
(Religion)

Performance

Science
(Arcana)
(Medicine)

Thievery
(Sleight of Hand)
(Stealth)

Wilderness
(Animal Handling)
(Nature)
(Survival)