Resistor E-series kit.
E12 10% tolerance
E24 5% tolerance
E48 2% tolerance
E96 1% tolerance
Bigger the number after E the more values you have (but not necessary per value, so that might be a trap some "shady sellers" might use.), but usually the kit get more expensive. With combining several resistors of these values to series or parallel you can make "any" value between that is not readily available. So you want a kit with with minimum 5 pieces per value, ten pieces is usual. Go "cheaply" on this, after all these are for to get started so try to find economic solution (not the cheapest nor most expensive).
Edit. --Removed some false information about size vs. wattage-- I newer have put too much thought on this physical size vs. wattage before and this started to haunt me after the post. So much I got to lift my stockpile to table to see. I have always thought it is someform of loose standard, but it seems I were wrong. It do depend the type and manufacturer it seems which dimensions the resistor do have not so much of the wattage (See picture). The smallest (as far as I know) 0.17W traditional through hole ones tends to be too thin legged, but they are nice for all sorts of squeesed inside a neclace type of prototypes/projects and easier to use on the fly than SMD parts.
The two lowest ones are what I have written down as 0.17 wats and these two are the only ones that are a bit thin for breadboard (if the board is well used). The next four resistors do have wattage ratings from 0.25 up to 1W. Red LED is 3mm and Green is 5mm type. Lesson, do not assume.
Don't go over with the transistor hording. NPN is more used in bibolars. Mosfets both N and P types as they are used mainly for switchs (another is normally open and another is normally closed switch). Get the a "handfull" of any cheap types also to just burn them up while toying around. Even germanium signal transistors from stoneage generally outperforms arduino style outputs in speed.
Get few nanofarad = nF = 0.xxx uF size range ceramics or a like preferably something on 30V or so voltage limit so you can throw them in to more varied applications than just arduino output.
Get a few electrolytics in 1 to 100 uF (microFarad) range, electrolytics are normally used as a ballpark figures so many times totally wrong sizes work especially if you go upwards. Get as small Panasonics or other better end low ESR type with values 1 to 4.7uF as they seem to be the common sizes for on chip charge-pumps (or tantalum / ceramic range of 1uF to 0.1uF). Get a one or two bigger 680 to 1000 uF (1000uF = 1mF) with 63V to 100V for test purposes. Like 2 680uF or 2 1000uF for powersuply filter / stabilisation caps use after bridge rectifier (reason for higher voltage rating = cost more).
Only a FEW leds, I prefer the 3mm diameter types (the typical 6mm diameter have usually better markings for anode and cathode). These are mostly for "I'm on or off" type of purposes in your drawer, for anything else you include them to your BOM for a specific project. One might get also a few cheap 7-segment display modules (invidual components) and maybe a driver IC for them.
Get a trim potentiometers a few sizes (blue burns are top notch and drop to breadboard nicely if you take ones with round legs). Get one 100 Ohm 500Ohm 1kiloohm 10k 20k 50k 100k ... maybe 500k or that range.. Get the ones that have the white trim area facing upwards while the pot is mounted on board you will regret if you don't even if you do find a cheap deal (don't ask how I know). Get one 2x6 rotational switch (some modest quality ie. cheap end ($2)
Lorlin 2 will do ) and make a box / stand for it.
Electromechanical devices are typically way more expensive than silicon, so these are the ones that are hard to decide which you need and which you not need VS. your budget.
Get some coil winding wire.. 30AWG or so max. (You only "need" it a few meters, so don't get that 100 meters spool) One source is old dumpster dived electronics, but these days it gets harder and harder to find, older laptop PSUs are transformer based (you know the type when you pick one up.)
For ICs.
Get a two 555 clock circuits just because.
Get a few LM358 OpAmps (or equivalent), there is better ones out there, but these are drop in replament for the classic OPA741 and are single supply compared to double supply 741.
Get 7805 Voltage regulators and one 7905 (maybe 7812) get the ones with a smaller package. If not sufficient (power rating) get bigger ones for the projects (if needed)
Get LM317 just for those powersupply tinkering projects.
Get get low-drop 3.3Volt regulator (unfortunately I do not have experience of these)
Anything else... hmm.. Get MAX232 serial adaptor IC.
Get one LM35 temperature sensor
Also locate the nearest physical shop (/shed) of electronics components, might or might not be handy.