The RAW in 5e is that if a material component costs money (like the 300 gp diamond for Revivify), you need to actually have the component. And if the material component doesn't cost money, there are two ways to get around the material component: you can assume that it's something you already happened to have in your component bag, or, you can use your arcane focus instead of the material component. (Of course if you happen to not have your component bag or your arcane focus at hand, but happen to have the actual material components, that's good too.)

I think this is a very good rule and I want to keep using it.

However I'm going to add prices to some of the components, for light-giving and food-giving spells. I want you guys to be starving and lost in the dark.

New players… I don't want them to be overwhelmed by all the rules, both RAW and house. Anyone who can genuinely convince me that they were unaware of this rule are assumed to have components enough for four uses of these spells and I'll also waive the weight requirement for those four uses.

In the RAW, this already costs 50GP, but then burns forever.

But now you can put in rubies of any cost, and then burns one hour for every GP that ruby cost. Like if you put in a 100GP ruby the time burns for 100 hours. So don't lose it. Rubies are tiny items (coin sized) even at higher values and you can also put multiple rubies into one casting.

A bit of phosphorus or wychwood, or a glowworm. Is a tiny item (coin sized) and costs two copper pieces.

Kept as RAW – no component added, you can have this for just the slot cost.

A sprig of mistletoe worth 5sp and is a small item.

Half the weight compared to a day's ration and feeds ten people instead of one? A good deal for one slot.

A firefly or phosphorescent moss. A six-pack costs 1 silver and is a small item.

Dry balsa wood. A six-pack costs 1 silver and is a small item.

Just because I missed them doesn't mean that they don't cost. Let me know and I'll add them here. Oh there is a 'Create Food and Water' w/o components? But it's a level three slot. That seems ok?

Generally, all spells that hit an area now affect a specific number of people. (This is an option from the DMG.)

The general formula is the area divided by five and rounded up. Except cones, divide them by ten. And lines, divide them by thirty. So a 100 long line can hit 4 people.

If it has been established explicitly that people are standing unusually far apart, subtract 1d3 and if they stand unusually tight&huddled together, add 1d3 to the number of targets.

Some spells and abilities I've created specific rules for. I do these as we go and so far it's four:

• In ordinary fight, no more than 5+dF (or 3+1d3) enemies and no more than 1 mêlée group can be lit just by moving through them.

Thorn Whip in ordinary fight:

• If you attack someone in another mêlée group, you pull them out of it.
• If you attack someone outside any mêlée group, you pull them into yours.
• If you attack someone in your own mêlée group, it's just another attack.
• You can also pull them into caltrops or similar, instead.

Thorn Whip in Chase or Volley works with the listed ranges.

Getting pulled out doesn't trigger opportunity attacks, the rule book says:

"You also don’t provoke an opportunity attack when you teleport or when someone or something moves you without using your movement, action, or reaction. For example, you don’t provoke an opportunity attack if an explosion hurls you out of a foe’s reach or if gravity causes you to fall past an enemy."

Ray of Frost in ordinary fight:

• if you are frosted, you can't run from one mêlée group to the next, but you can move into mêlée groups if you're out, or out of mêlée groups if you're in
• if you aren't frosted, you can move between mêlée groups.

Ray of Frost works best in chase or volley, where it works with the listed speeds.

Moving between mêlée groups on your own (if you're not pulled), that triggers opportunity attacks.

(BTW, shouldn't being encumbered work like being frosted?)

(BTW, Healing Spirit saw an official nerf on Crawford's Twitter — they don't like changing the game so they framed it as "a suggested houserule". But, I think with clear rules for targets in areas of effect it's not needed.)

• In an ordinary fight, you can move in and out of the spirit using your movement. Remember that joining up large mêlée groups in order to take advantage of the Healing Spirit enables the monsters to sidestep the three-medium-per-target limit.
• Outside of ordinary fight, only one person per round can be healed. So the ten d6 are divided up among the persons to be healed. This brings it about on par with Prayer of Healing.

(This is neither Haeck's nor Crawford's suggestion but is similar to the commenter FeyPhoenix on D&D Beyond. Seems like we had the same idea.)

As per Veins, there are six routes, see Climbing.

This is a level three Thief feature. You gain two additional benefits, in addition to the ones listed (faster climbing speed and longer jumps).

• Your DC is halved for routes 1, 2, 3 and 4.
• You are allowed to attempt routes 5 and 6, but with normal DC.

You can run along routes 1, 2 and 3 without rolling. If you end your movement there, you need to climb in order to grab hold.

These abilities are stolen from an OSR-game, GLOG by Arnold Kemp. I wanted to buff the assassin a little bit!

Starting at 9th level, you gain the ability to create false identities for yourself. At any time, you may declare that you are walking off. Later on in the session, you may reveal yourself to have been a minor NPC in the background “all along” as long as there actually are minor NPCs present. You can walk back on at any time, even climbing in a window. This ability is limited by plausibility. You can't have been seen at the same time as the NPC since they are (retroactively revealed to be) an alternate persona you've created and maintained. Creating a persona like this costs 25 GP and 7 full workdays, but, you can pay that retroactively, after the reveal, by removing any 7 days from your character's past and by paying 25 GP. (However, if you neither have spent 25 GP in the past nor have it available now, you can't use this ability.)

At 13th level, you no longer have to create personas for your Infiltration Expertise, you learn to replace pre-existing people, body snatcher style. You need to study them for at least three hours. This doesn't cost GP.

This is not RAW but it's a houserule. The patrons of warlock are cruel and have decided that:

If you have the invocation Agonizing Blast, then:

• Eldritch Blast scales with your warlock level, not your character level
• You can't use other metamagic such as "quicken" on that spell

• Take the bonus action in advance, pre-emptively. This is just like the RAW, but that's worth pointing out here because we have a house rule allowing people to spend their upcoming main action in advance to dodge.

Already the best feat but I'll add a buff to it. Instead of learning a level 1 spell, if you go Cleric, you can learn to create holy water (see equipment list PHB p152).