Really like these:
Elite Submersible Preset Heater Mini 25W
- I use this in all my smaller tanks, it's adjustable which is great. Should be paired with a thermometer.
- These nifty plants sit on weighted spheres so even if you don't have them buried in substrate they stay upright but don't float. They are pricey but their quality is better than cheaper brands.
Jardin Silicone Aquarium Fish Tank Sea Anemone Ornament
- My bettas LOVE these, my big halfmoon boy stuffs himself in between the tentacles to sleep. It's hilarious.
Topfin Aquarium Gravel in River Rock
- WAY better than their other types of gravel! The stones are smooth and I've noticed they give off less dust after an initial cleaning than other types at the same price. They're also not coated in weird synthetic colorant crap.
API Freshwater Master Test Kit
- Has everything you need to test your aquarium, super easy to follow instructions that even a beginner can understand perfectly well.
Seachem Prime Water Conditioner
- The best water conditioner on the market!
Seachem Flourish Plant Fertilizer
- I don't have a substrate in my planted tank, just gravel, and my plants are thriving thanks to this stuff.
- This stuff is fantastic for a cloudy tank. Just be aware that while it will fix cloudiness, it won't fix the underlying problem making the tank cloudy to begin with. It should not be used in place of water changes!
- This is a live food that is super low maintenance, you can find a culture online. Live foods provide the best benefits for fish. Grindal worms are small enough to feed to juvenile fry and adults like them too.