Every list of homemade fertilisers mixes together three quite different things: materials that genuinely feed a plant, materials that only help after they have rotted down, and things that should never go near a pot. Sorting them is more useful than collecting them.
Worth doing
Fish tank water is the best of the lot. It carries dissolved fish waste and a low, steady nutrient level, it cannot burn roots, and the tank needs changing anyway, so the cost is nil. Use it on anything that is growing.
Rice water is the second one, with a condition. It contains starch, some protein and vitamins, and poured fresh it does very little beyond wetting the surface; left standing a day or two until it ferments and then diluted, it becomes a mild feed that the roots can actually take up. Undiluted and daily, it leaves the surface of the mix sour and crusty.
Eggshells are calcium plus a little protein residue. Rinse them, dry them, and crush them to a powder rather than leaving them as halves on the surface, because a shell the plant must slowly dissolve in the pot is doing nothing that year. Powdered and worked into the lower part of the mix, it is a base dressing, most useful on acid media.
Bones are the same idea with more phosphorus behind it. The traditional treatment is to steam them under pressure for about half an hour, dry them, then grind them and mix them with coarse sand for a base feed. What you get is a slow phosphorus and calcium material rather than a balanced fertiliser, which is exactly what you want at the bottom of a pot for a plant that is meant to flower.
Oil seed residue, the cake left after pressing sesame or other oilseed, is the classic orchid feeder and one of the few genuinely rich organic materials safe to use in a pot in small quantities. Every two weeks during growth, in weak pieces rather than a handful, is the usual rate. Fresh, unfermented and in quantity, it heats as it breaks down and damages the roots it was meant to feed.
Only after it has rotted
Fruit peel, vegetable leaves, tea residue and herbal medicine residue are all good material and all wrong fresh. Bury them while they are still raw beside a root system and they rot down inside the pot, drawing nitrogen away from the plant as they go, and their decay smells and invites fungus gnats. Compost them first, or place them in the lowest layer of a deep pot where nothing important is rooting, and use tea residue sparingly: a thick layer of it compacts the mix and the roots suffocate in it.
The same rule in sharper form applies to spoiled milk. It is a real fertiliser and it will burn roots at full strength; dilute it well, and do not make it a habit, because the sour residue on the surface is a mould farm.
Traditional, but do the arithmetic
Onion skins steeped in warm water for a few days make a weak trace-element drench, and diluted beer wiped over large leaves lifts the dust off them, which is probably most of the benefit either one delivers. Neither is a feed in any sense a plant could rely on.
Wood ash and mosquito coil ash will supply potassium and lime to an ornamental pot, and they are genuinely useful on that basis, but ash is strongly alkaline and repeated applications will shift the mix out of reach of any acid-loving plant. Coil ash also carries whatever the coil itself contained, so keep it away from anything you intend to eat and away from seedling trays.
Skip
Waste cooking oil. It is still recommended in some places as a slow feed for woody pots, and what it actually does is coat the soil particles and the upper roots in a film that water will not penetrate, while going rancid in the pot. There is no mechanism by which it helps.
Household materials are soil conditioners with a small fertilising effect attached, not a substitute for feeding. The question of which of them to bother with, and how they sit alongside a measured mineral feed, is the argument in organic versus inorganic fertiliser, and the schedule that decides whether any of this is applied at all is in how much to feed and how often. If a plant is yellowing rather than merely slow, diagnose before you remedy: the pattern is read in which nutrient the plant is short of.