Unwanted post. Please delete.
.. dont forget all the "bread&butter" modules you are going to need (f.e. buffered multiples for non-audio (LFO, ENV), many attenuverters - (attenuate, damp, invert, shift/octave) for propper "positioning" of your modulation-signals before going into your Boutique-modules -, mixers, aux-ins (from line-level) aux-outs (to line-level) for propper gain-staging.
Try get a bunch of stackcables (TipTop) for splitting signals (not merging!) easily - you are going to need one modulation-source sent to different destinations. Following your signal-flow (mental) will be easier this way.
But most of all I would advice you to get the THREADED STRIPS /rods instead of the M3 -nuts which usually come with your rack. Try searching for "eurorack threaded strip".
Otherwise positioning these M3-nuts correctly underneath/behind your modules will drive you "nuts" - and getting the last module in is a real puzzle. You will change the position of your modules in the beginning very frequently. These strips help a lot making it painless.
.. and the one power-unit in the lower left corner will not be adequate at all if you are thinking skif-shape.
First of all ... welcome to your new addiction!
You will start as we all did. You want it all. All these shiny tempting modules. But after a few days and weeks of consideration you will be starting to get a more realistic approach - and thats good. Since you are not Hans Zimmer, you will not have the money to buy all these modules at once - and thats good too. You will start scaled down a little bit. And most important is, that you understand, that starting to deal with modular you have to get "under the hood" much more, then you would have to, if you just simply would buy a plugin. See it like building a house. Knowing which color your roof will/should have in the future may be interesting, but thats not where to start. First of all make yourself familiar with the "idea" behind modular, which is - modular.
Combining things to become something thats not available our there. Get an idea of what you want to do as musician/sound designer. You want keyboard, you want sequencer, you want automatic music ? You have to find out. You can find out. You have the pleasure to find out - since nobody knew, when he started. Its signal flow. Its influencing. Its being influenced. Its mixing. Its mangling. Its using things for other things they where not meant to - but since its modular its "allowed". Everything is right. And thats the pleasure and the pain at once.
So I would suggest to make yourself familiar with the idea of modular. And since everybody can only give the advices he for himself knows the best, I can only tell you how I did it. And I started virtual first. Why? Since you know absolutely nothing at the beginning. And since you have to learn everything from scratch, its best done without massive investment in things you later will learn you dont need. I started with a software that comes from a Swedish company called Clavia Nord. They built a synthesizer over a decade ago that was "virtual modular" and it was called the Clavia Nord Modular G2. The neat thing about this software is, that you do not need to buy the synth, nor the software. There is a completely free demo-version available on their homepage. Search for "Nord Modular G2 Demo" and you will find it. You can pull modules (for free) and patch them.
Get a VCO and combine it with an VCA. Connect a LFO and modulate the volume. You will not learn why you need attenuverters, you will find out and then know.
Start as everybody did before you, - and everybody after you will too ... if really interested in it. Just do it. Buying Boutique-modules just brings you to a certain level. Impress friends and strangers. But you will have to learn how you can influence these modules with modulators (control signals; control voltages; CV) and this then will free your mind - and this will impress yourself.
Let the tide play the flute. Pitch it up by 12 octaves. cross-modulate it with the wind, and use the rectified signal of it to clock the melody of a glacier with it.