FRPG alternate rules

 Abstract wealth:

Wealth is measured in abstract coinage. If you want to buy something, you compare its price with your coinage. If the price equals your coinage, you buy it and lose a coin. If the price is one less, you buy it and lose a coin one third of the time. If the price is two or more coins less, you just buy it. You can't afford anything that costs more coins than you have.

Adding treasure works similarly. Anything worth less than one coin than you have doesn't add to your wealth. One coin less will add to your coinage one chance in six. Treasure equal to your coinage increases it half the time.  Treasure one coin higher than your current wealth is increased one chance in six.

When using slot based encumbrance, your coinage occupies 1/2/3/5/10 slots. When using pounds, your coinage weighs 1/3/10/30/100 pounds. More than that and you need a wagon or magical container.

Alternate spellcasting: 

Slots and checks in a d20 system.
(Spells have tiers instead of levels to avoid confusion.)

Use the spells per day charts. Casting those spells doesn't require a check, but does use the slots. Daily renewal of spell slots requires a minimum of 6 hours of sleep plus one hour of spellbook study or prayer.

To cast additional spells, the caster makes a spellcasting check at
DC 10 + twice the spell tier. Their casting bonus is their spellcasting level plus stat bonus.

If a caster fails a spellcasting roll by 5 or more, they cannot attempt to cast that spell again until after a full turn of uninterrupted spellbook study or prayer. If they fail by 10 or more, they can't attempt spellcasting checks of spells of that tier or higher until after an uninterrupted hour of spellbook study or prayer.

If a caster makes a roll by 10 or more, something good happens. Examples: Spell is upcast, damage/healing is rolled with advantage/maximized/doubled, spells affects triple the usual targets, spell duration is tripled, area of effect is doubled, allies/enemies in AOE are ignored, caster gets to choose instead of rolling on a random chart, caster regains a used spell slot of that tier or higher, caster heals the spell's tier in hit points...

Cantrips are tier 0 spells. Cantrip checks are made with advantage once the caster gains a tier 2 spell slot. Read Magic is a cantrip.

Caster can attempt to cast a known spell of one tier higher than their chart says they can, but the check is made with disadvantage. Failure by 5 results in the loss of half the spell's tier in hit points.  Failure by 10 results in the loss of the spell's tier in hit points.  These are in addition to the usual penalties.

To upcast a spell (when allowed), either use a higher tier slot, two equal slots, a slot and two of the next lower slots, a slot and a check, or disadvantage on the check.

Turn Undead is a cleric spell-like ability, where the DC is 10 + twice the target's hit dice. For every point the check exceeds the DC, one additional creature (of that DC or lower) is turned. Succeeding by 10 destroys the target, with an additional creature destroyed for every point higher. Failing by 5 or more results in the cleric not being able to attempt to turn that creature again until after an uninterrupted turn of prayer. Failing by 10 results in the cleric not being able to turn any creatures of that power or higher until after an uninterrupted hour of prayer.