Try ton convince your parents to order online, you can get stuff much much cheaper. For example, you can make your own Flourish Potassium. Order potassium sulfate, and mix 1.4tbsp with 500ml of water and you get the exact same thing for 1/20 the price.
The PlantGuy- Canadian Aquarium Plants
And here is my advice for your plants.
Liquid carbon (like Flourish Excel) is not a fertilizer, but it is very useful for plants. Use it.
The nutrients that plants need are NPK (nitrogen, phosphorus, potassium) and a mix of macro elements like calcium, magnesium, iron...
Nitrogen and phosphorus is introduced with food and fish waste. Your tap water probably contains enough calcium and magnesium. But there is no potassium getting into your tank, so in my opinion it is the most important nutrient to dose.
In addition to it you can also dose a more complete product like Flourish (also called Flourish comprehensive).
Or if you want the best fertilizers for your plants, do a search for Estimative Index.