Hello there! How's it going?

There's a few ways to go about making PC, but this is a rather slow game without much inflation (yet)
With that in mind, here's a few tips:

1. Log in every day. You get up to 7 PC per day just for logging in.
2. Sending your Pet on hoards. Evolved pets bring back double the coins.
3. Growing and selling extra products -Pumpkins and plants are always in demand, the higher their grade, the more they're worth.
4. Baking Evobars - Very time intensive, but worth quite a bit. Can be sold at auction.

If you're an artist, you can do commissions for currency as well.

There are also plenty of rare items and eggs that can be found on hoards and sold at auction. While by no means a complete list, this is what I do and I hope it gives you a good start. :)

@Wintersolace
Since I just finished writing a list for a slightly similar thread, I figure I'll post it here too! However this list describes literally every way to make money in Pixpets (that I remember), so some of them are not necessarily the best methods. Also some of these have been mentioned already by the cool peeps above me, but that just means they'll stick in your mind better! :p

Item Auctions - You can place an item up for auction via the Item Inventory (Items tab > Item Inventory); it's one of the buttons near the top of the page that's labeled "Add to Market". By clicking this, each item in your inventory will now display several buttons that allow you to set the starting bid, auction length (in days), and quantity of the item. Once you've set these, you can click the "Add to Market" button to the right, and then it's placed on the public auction house!

Item Sellback - This is another button within the Item Inventory that's near the top of the page, and simply labeled "Sellback". Selling items back to the server will give you very small amounts of PC, typically 1 PC for non-decoration items, and varying amounts for decorations (but still not much). How it works is pretty straightforward, but if you have questions anyway I'd be happy to answer.

Usershop - You can add stuff to your usershop (which is displayed on your profile) by clicking another button near the top of your Item Inventory, labeled "Add to Usershop". Note: the only way that people are going to notice your usershop is if you advertise it in the forums (via Dealers Den) or on the Discord server (via #market).

Egg Auctions - Similar to item auctions, but instead you're going to find the option within the Pixpet Inventory (Pixpets tab > Pixpet Inventory) and it's a button labeled "Pixpet Egg Handling". On the Egg Handling page, you'll see the sorting options. Underneath these are three buttons; the one that you want is "Add to Market". Once clicked, you'll see buttons next to each egg that are nearly identical to the item auction buttons. The only thing missing is the quantity buttons, since you can only auction eggs individually. Set your desired parameters like usual and then click "Add to Market"!

Egg Sellback - This option is also located on the Egg Handling page, and is the leftmost button labeled "Return Egg". The sellback price for eggs is shown within the button next to each egg. If you have a lot of eggs, this is going to be your favorite of the sellback features.

Pixpet Lottery - Also known as pet interactions. Players who have at least one available pet (not on a hoard) will display a "Play Lottery" button on their profile. When you click this, you'll also have to click a second button "Give to <insert name>'s pets" in order to complete the interaction. You'll be awarded with either pixcoins, plant seeds or food pellets.

House Auction - You'll probably only use this to sell the house that you just moved out of, unless you want to flip houses. The option is located under the Housing tab > My Houses, and select the house that you want to put on the market by clicking its sprite. Right below the house part overview is the Market option. Auctioning a house is a bit unique compared to auctioning other things because there's a 10% fee to list it. Be careful here because if you overprice your house (say, twice what you originally paid for it), then you'll pay an expensive listing fee, and your house may not sell, which means wasted money!

House Sellback - I wouldn't recommend it, but it's an option. This is located on the same page as the house auction option (Housing tab > My Houses > click the sprite of the house you want to sellback) at the bottom of the page. The server will give you 50% of what the house is worth. It's more profitable to auction a house, but if you need PC immediately for some reason and have an extra house, this'll do.

Gaining badges awards you 10 PC for each badge. There's a guide by Krill (link) that explains how to get each badge. You can also check the Pixpet wiki for the same info.

Referral System - If one of your friends signs up, they can add you as a referrer, and you'll receive 10 PC for every badge they earn. It may not seem like a lot, but if you have a lot of friends who like petsites, then this has the potential to bring in a lot of PC.

Player Services (via the forums) - Such as art commissions, evobar-making services, potion-brewing services, etc.

Login Streak - You'll gain a small amount of PC for logging in each day, which will cap at 7 PC. If you break your login chain, the reward resets to 1 PC.

Aaaaand hoards! Evolved pets will double (or triple, for twice-evolved pets) your coinage. A Wealth Potion can also add on to that (up to 50 PC for a grade 100 potion).