my group never keeps track of xp or gold. this was a mild ongoing frustration for whoever happened to be DMing at the time.
over time we tried a bunch of different ways of hacking it;
-simple numbers - minions worth 1 xp, bosses worth 2-5 xp
-carousing xp - 1000 xp for every 1000sp wasted in revelry
-DM's discretion - DM would regularly just award levels when the time seemed right.
eventually we landed on these two systems: simple xp and simple currency
after a bunch of fine tuning, +Jack Mack came up with this system.
numbers are crunched at the end of a session; any leveling up happens at this time.
+1 xp for playing in a session (survival xp)
+1 for getting a significant treasure or magic item
+1 for carousing a significant amount of currency
+1 for dealing the finishing blow on a boss
+1 for succeeding at a critical moment despite risky odds ("big balls xp")
this isn't a perfect system since it still requires numbers to be tracked, but it seems to have been working for us.
XP requirements increase exponentially
amount of XP required to level up = current level^2
XP total doesn't reset after level-up - keep adding to the same number
level 1: 1
level 2: 4
level 3: 9
level 4: 16
level 5: 25
in a highly productive session, a player might expect to get +4 xp.
+1 or +2 xp per session is more common for chiller sessions with fewer hell-demons
the numbers eventually get quite intimidating, since our group generally keeps the level cap pretty low. my highest level character to date was an 8th level elf warlock, Sebastian. the highest character i've ever partied with was Stoner the astrologer, a 9th level fighter. boss NPCs tend to be anywhere from level 8 - 11.
recently, instead of tracking a large number of gold and silver pieces, i've been handing out little blue and green game tokens as currency. the blues are worth $1 and the greens are worth $3.
each player is responsible for keeping track of the physical game pieces awarded to them (informally dubbed "groves dollars"). forgetting to bring your pieces to a session means that your character left their wallet at home.
currency is treated like a stat, and rolled for at character creation. humans automatically roll 3d6, all other races roll 1d6
(optional rule: ...unless their cha modifier is at least +1. if so, roll 3d6)
like any other stat, your currency stat has a modifier, which indicates how wealthy others perceive you to be.
(+4) royalty or equivalent
+3 - elite upper class
0 - middle class
-3 - impoverished lower class or refugee
(-4) - slave, unclean one
high-quality items cost $1 (a sword, an ornate pocket watch, a fine suit of clothes)
for low-quality items, I give my players 10 seconds per $1 to write down what they can get. Informally, $1 will buy a large sack of miscellaneous gear (rations, torches, adventure stuff)
a level 0 hireling costs a one-time payment of $2 dollars. a small house in the cheap part of the city will cost a one-time payment of $3. $1 can be spent to add +1 to a 2d6 charisma check to bribe someone.
a wealthy king will likely have about $20 on him; a dragon's hoard might contain $30. a $5 bounty might be placed on a wanted criminal, split between the party members.