I have 4 online business/websites/products and not sure where to start

First off I have been a lurker here for a while, always reading and studying and now I finally posting something. I really value the advice in here so I am ready to receive some (if you please)

So these are my four things. I have never paid for any ads or marketing for any of them and I am ready to now (I just wasn't invested in them and now I have heaps of free time so I am ready to roll) and I have some cash to spend on ads etc (a couple K at the moment but can get more soon but want to limit what I spend to begin with)

I will warn you it is a bit long - each one is broken down to explain what it is.

1st: Website - clothing label that has no stock (this is my main focus - I have two factories overseas who make all the clothing as they are ordered - so it kinda drop shipping. I have a huge market for this (basically any woman who shops - we have no size limitations or age) as we have a special concept so only a handful of competition which is great. We are about to launch a huge campaign in 3-4 weeks and also now we have built up the mailing list to about 5k we want to start doing flash sales every day. I am revamping the website because it runs slow at the moment. The photos are too big in size. I only want to sell from the website. I have no facebook for it and a very small insta account.

2nd - Apart from an upcoming photoshoot next week, this product is ready to go. It will have its own website. Only sold through there and maybe Etsy and Amazon. It is just one product - a piece of clothing (pants to be exact) that I have a very unique design for(kinda comfy at home pants that stretch but look nice). I have been planning to do this for years, I made tens of samples and tested them out with friends and had amazing feedback, just never had the time. The person making them and dropshipping them is doing it exclusively. Really high turn over each one I sell.Super easy to market - they are going to be very affordable ($25) and easy to buy (sizing really simple) and it needs to be marketed at targeted woman.

3rd - Childrens book - we have the stock ready to go - my daughter and I self published a children's book (link removed) just for fun last year and now that the family and friends sales have died down and we have 400+ books just sitting around I really want to start pushing it and getting them out. We have a website and it for sale on Amazon, Etsy and Print on Demand. We do offline marketing with it, like she goes and reads at schools and libraries but that is about it. Never done any advertising for it, just some Instagram posting thats it. We have small publishers contacting us to pay them a set amount and they will promote it and distribute it but I would rather spend the money and do it ourselves if I can.

4th - another clothing label that I run exclusively through Etsy that has been running for 5-6 years. Again no stock and everything is made to order. I do have a website but never used it, just have it there for google search. This label is more focused on custom halloween outfits and comic con but I do get 10-20 normal non halloween/costume sales a week too. I want to be pushing this during summer in preparation for Halloween and Comic Con. I do use their google ads within Etsy and spend a couple dollars a day and I push this up to $10 during Halloween.

sorry again for it being so long. I am feeling anxious about breaking these all down and working out theses best way to spend my money on advertisting them

Basically 3 of the 4 are targeted at woman
and the last one is targeted at moms with kids?

I am undecided whether I use instagram marketing or facebook, adsense all of that. I have never had to do it before! I am glad I have everything set up now I just feel a bit lost on what to do.

Thanks for reading too!