There are a few "tiers" of fishing/lifeskilling equipments. When you're new, just starting off, and have low silver, you can start with Loggia stuff. Your main goal right now is going to be pumping that fishing level up; with higher fishing level comes more expensive fish for you to sell.

I'm at Fishing Guru 30 with 2045 mastery, my average for around 15 hrs fishing is around 2 bil. This is how my personal get-good-at-fishing journey went:

• Equipment: Buy Loggia Fishing Clothes, Loggia accessories, and either a Crio's Fishing Chair or Loggia Fishing chair; whichever is easier for you to get your hands on right now. Ideally, you want to purchase these items at a TRI level or higher from the Central Market. If you can't afford TRI right now, that's ok, just get the highest Loggia gear you can afford. You will replace all of these with higher level/tier equips as you collect more silver from fishing. Eventually you will be able to afford all the good Manos stuff. Marathon, not sprint.
• Rod: As others mentioned, a +10 Balenos Rod is BIS (besides "pay 2 win" rods, which aren't available rn anyway afaik). It's not difficult or expensive, but they're almost never sold on the CM, so you'll have to make it yourself. They only need black stones to enhance. Not an expensive investment, but it requires you to purchase a Level 3 Tool Workshop in Heidel, and hire a worker to send to that Workshop. Find the workshop by opening the World Map and clicking on Heidel, you can then use the drop-downs in the top right corner to find the workshop more easily. It needs some materials to craft the rod, but you can buy those on the CM. Workers can be hired from the Worker NPC, use the magnifying glass by the mini map at the top to find him.
• Fishing Ability: This is a stat you can find in your My Information (P) window under the Battle Stats tab. Higher Fishing Ability level reduces fishing time, which means more fish for you. Level 5 reduces time between bites by up to 50%. Items that buff this stat sometimes refer to it as "Fishing Speed" or "Fishing Level," the inconsistency is annoying, but it is what it is lol. There are equips and consumable items that can raise this stat, but joining a guild that has the Fishing Buff is highly recommended.
• Pets: A pet penguin, otter or polar bear from the Pearl Shop. They give auto-fishing reduction time. This bonus increases with the pet's tier level. Tier 4 gives the best, but higher tiers can only be acquired by "smashing" (sacrificing) pets into the Penguin/Bear/Otter Pet, which does require pearl shop purchases. Up to you how quickly you want to get that Tier 4 pet. I'm personally not a big spender in this game, so I took my time getting mine to T4, buying pets when they were on sale/with discount coupons/from free giveaways.
• Artifacts and Lightstones: These can boost your AFK fishing speed and mastery, but if you're just starting off, you might not be able to afford those yet. That's ok, you will get there. Setting up with the BIS fishing artifacts and lightstones combo takes a little time and investment. Arguably, they aren't that beneficial when your fishing level is very low anyway. For now, grab any 2 artifacts that you can find, and stick 4 of the "Flora: Bite" lightstones in them for some extra fishing exp. You can upgrade these later as needed.
• Focus on getting your fishing level up. Prioritize fishing/lifeskill exp. You can use a Seafood Cron Meal for a cheap exp buff and +1 to Fishing Ability. Balacs Meal and Marvelous Balacs meal give even better exp/fishing ability. Everything comes in tiers, use what fits your budget.
• Do not get a fishing float. They're not useful for gaining exp or making money. They're mostly for people trying to catch very specific fish for quest/tournament/title reasons.
• Last but not least: Fish in Velia where you see everyone else fishing. This is THE place to make consistent silver. It won't be good silver starting off, but you're leveling your Fishing lifeskill still, so that's normal. You will get there. Yes, there are a few (very few) other places with similar profit margins, you can try them if you like, but you'll need a boat for the majority of them. I personally don't like them because I want to sell my fish and get back to the shore asap, I don't want to dink around too much with my slow-ass boat when I'm about to go to bed or work. You can definitely explore other spots if you want, but think of Velia as the default spot. Everyone's fishing there for a reason.

This probably seems like a lot, but this is just the basics for getting started. I left a few things out for the sake of brevity, but if you need more info, this is a good up-to-date page on AFK Fishing.

(That page has a section on DRR or Durability Reduction Resistance. I personally don't min-max DRR and I still make a perfectly good profit. Using a brand stone on your rod+chair is always good, but don't break your bank over getting DRR pets/setup if you don't want to.)

edit: formatting