Red Dead Redemption 2

This is my first ever solution for anything. Be gentle, ha.

First, how to do actually do this.
In order to complete this trophy you have to purchase the 4 additional horse stalls at the stables as well as fill them with horses. The purchase amounts for each are $100, $150, $500, and $750 ($1,500 total). The gold bar amounts are 4, 6, 20, and then 30 bars respectively. I personally used gold bars that R* gifted for the 4th and then grinded for the 5th one. Once you have them all open, fill them with Kentucky Sadlers for $50 a piece ($200 total). Don't purchase any in the empty stalls until you have enough money for all of them as it adds to your daily stable fee (small but nonetheless unnecessary).

*Edit* - with the May 2019 update, R* claims that more revenue should be generated in general from activities. I also do not know if the stable amounts have changed, as I not only have them all unlocked but don't play this much any more. I nonetheless think this is a solid guide and should be helpful on knocking this thing out. The amounts stated here were as of the February 2019 update.

Now my general advice on how to go about saving up for this bad boy....
1.) Unless you're willing to put out about $10 cash out of your own wallet, this is going to take a while. Be patient, and do your best to actually enjoy the game. You will definitely get this on your grind to rank 50.
2.) If you have not completed the main story mode, I would advise to do so. The mission Kill Them, Each and Every One nets you over $200 alone and the other missions will make you some dough also. This is also a decent way to rank up a bit. *Note* there are actually a few story missions that you need to have bad honor in order to do (though you don't have to do them in order to get to the $200 mission)
3.) Make certain to seek out the treasure maps that are given every 5 ranks at the post office. They will net you $75-$150 per map, and you level up fairly quickly in the first 20 ranks. There are YouTube videos on many of them if you're struggling finding the chests.
4.) Do not buy unnecessary goods (clothing primarily). NEVER buy a canned good or item to restore your cores when in free roam. Always cook meat you obtain in the wild (I suggest big game + mint, oregano, or thyme to amplify your cores) and then store them for later as even the smallest meat gives much more return than any canned item could. Sometimes I'd buy an apple or carrot or two for my horse, but the wild carrots you can pick give as much core value as these do (and they're free, of course). If you need a quick dead eye core fill for PvP, pick up some cigars.
5.) You probably at some point will buy certain guns to obtain perfect pelts, as well as be decent at PvP, understandably. I recommend picking up the varmint rifle ASAP if you're new as it's necessary as a hunting weapon for smaller animals/some birds and great in PvP as well. After that, I suggest the bolt action (for deer/elk/wolves/alligators etc., decent in PvP), the bow for small game (one of the least expensive weapons too), and possibly the Lancaster repeater (my favorite for PvP) if you just hate the varmint rifle in versus. If you're just hankering for a shotgun, I advise the pump (though picking this up really isn't necessary to fair well online). Personally I would wait for the bow until at least rank 22 when you can buy the small game pamphlet, as it's not the best for PvP and you can get perfect pelts with the guns mentioned above that you could use a regular arrow for. Other than these, I would avoid other gun purchases.
6.) For a while I held onto a ton of meat. Eventually I realized this is pointless, for three reasons: 1) You can sit down at a fire to cook and stow 10 big game meat + a few of another meat and be set for a long time 2) by not selling meat, you're wasting inventory opportunity because once you have a max of 10 of each type, you can't carry any more and as you skin animals you're not being given their respective parts that you should be. 3) some meat (venison, plump bird, and game meat) can go for $.50-$.60 a piece, which can mean $5-$6 per type additionally to the pelts, feathers, carcasses you're selling to the butcher.
*Edit* - again, as of the May 2019 update, these prices may have changed.
7.) upgrading weapons online is EXPENSIVE. I would strongly advise against upgrading anything that you're not going to use specifically for PvP as that's the only time it could really help anyways. Really, I would advise to hold off on any until you get this stupid trophy out of the way, then you can spend your money any way you want.
8.) As for grinding for money... In PvP pretty much any game type will net you a certain amount of cash as well as a few cents towards your gold bars. Races pay out the least in my experience unless you win, which can be tough to do. If I do decent in something like Most Wanted or Pick Your Weapon I usually make around $11 a match. Stranger missions will make you around $15 if you wait until the timer is less than 30 seconds - look for Angus, his missions give the most XP and moneh. If you fish for salmon they make you $2.50 a piece (as of the February 2019 update) and so if you get 10 of those that nets you $25 (good spot at Whinyard Strait by the bridge). If you kill a pristine deer, don't skin it, just sell the whole carcass. Bucks will give even more back than a doe (females). Spoonbill, egret, and heron plumes all make you fairly good money (though can be hard to find). I recommend this Reddit post for various prices on animal products so you know what you're working with: https://www.reddit.com/r/reddeadredemption/comments/a1s8w8/o....
To tag onto this last note, find out what you enjoy best/are good at. This is a fair amount of money to save up for and does take some time, so if you love the PvP, play the heck out of the PvP! If you love hunting, hunt! My advice would be to spice it up and mix between fishing, hunting, stranger missions, and PvP once you finish the story in order to keep things fresh and prevent burnout.

As I said before, this is my first solution. Please feel free to comment on how I could make this better and I will certainly do my best to fix it.