For the question 'where should I invest my money', I have a one-word answer: Infrastructure
To elaborate, you spend money make money. You invest in being able to expand your business, and build ways of increasing profits. In SDV, that means Quality/Iridium Sprinklers, the occasional Scarecrow, and of course, Preserves Jars and Kegs. But to take advantage of the jars and kegs, unless you plan on lining the bus tunnel or something, you really need a place to put them. For this, there is no better building than the Shed. Plus you can upgrade the shed later on for even more production.
Here's the thing: In SDV, if you don't just want to fish, your best method of making money hand over fist is by growing crops, and processing them into either preserves or wine. And the more processing capability you possess, the more profits you will reap in any given season.
Now, with two coops and eight chickens, and planning on joja route, here's some things to consider:
* Mayo. White is the new green. It's pretty solidly profitable, particularly when you can reliably get Large Eggs from your chickens for gold-star mayo. Getting 3-4 mayo machines will dramatically increase your profit-per-chicken. I'm not sure what the numbers are in 1.5, I'm given to understand that the price of duck feathers has gone up to make them less of a trap, but at least in 1.4, they were probably the most reliably profitable coop animal. So, let's work with what you've got. You'll need a Copper Bar and an Earth Crystal per mayo machine, plus some wood and stone. You may have to go mining to obtain the earth crystal and copper if you don't have it already. I tend to go for a 1:2 ratio for convenience, one mayo machine per two chickens. That way in the morning I can load them up, then in the evening when I come back to my farm, I pull out the mayo and put the rest in. It's not the most numerically efficient, but it is easy to keep track of. With eight chickens producing large eggs, you can expect returns of (285*8) 2,280g/day just from the chickens you already have! And that's *without* the Artisan perk, which is a must-pick for anyone planning on going the Joja Route.
* Crops. You want them. More importantly, you want crops that aren't a continual drain on your resources every day. Which means sprinklers. And you'll want many of them. My initial setup is generally 20 Quality Sprinklers around a single scarecrow, for 160 crop plots automatically watered. Which crops will depend on which season you are in and which year you are in. The big thing is that you're not wanting to just sell the crops raw, you're wanting to process them to sell, which means Fertilizer is useless to you, as the quality of the crops is irrelevant to the profits you will be making. Speed-Gro and its Deluxe version might be quite useful to you, depending on what you are growing, but not always. If you want to simplify things, don't bother using anything on the ground, just plant crops, and process them.
* Processing. Kegs and Jars. If you want prodigious profits, then properly prepare your produce for packaging. For low profit, multi-yield crops like Blueberries and Cranberries, use Preserves Jars to dramatically increase your profits! For higher-cost crops like Melons, especially for fruits, brew them into Wine. It'll take longer, but the profit margins will be worth it. Special shout-out to Hops, which is brewed into Pale Ale in a keg, and does so in a mere two days. Needless to say, this is how you should process hops. But you're going to need these in bulk. Like 60+. Which means you need a place to put them. It also means you need LOTS of Wood and Stone. Preserves Jars also require 8 coal each, which isn't cheap, and Kegs require both Copper and Iron each. You're also going to need Oak Resin for your Kegs, so if you don't have an oak stand tapped yet, put that on your to-do list as well.
* Processing Facility. Unless you want to line the bus tunnel with kegs and jars (which is a legitimate strategy), you're going to need some sheds to put all your kegs and jars in. You can fit 60 in a shed, 120 in a Big Shed. These also aren't cheap, but your chickens right now will carry you on the price tag until you can get your produce processing properly.
* Joja Upgrades: Until you get your basic infrastructure set up, I wouldn't suggest getting any upgrades from Joja except maybe the bus repair so you can get Oasis seeds (especially Starfruit!). Once you do, however, especially if you have found an Ancient Seed, get your Greenhouse unlocked. You'll want 4 Iridium Sprinklers, then either another two of them or four quality sprinklers to maximize planting space. This is your path to making a million per season, year in and year out. You'll need at least one Seed Maker. Plant your ancient fruit on Deluxe Speed-Gro, when it fully grows, put the fruit into the seed maker. Rinse, wash, repeat until the greenhouse is full.
That should get you started, at least.