Congratulations on getting into the hobby. Having a 75 gallon is an amazing start if you have some knowledge on fish keeping. There is a big advantage on having a big tank however there are disadvantages as well.
to make it simple. A large tank you do not have to do as many water changes for example and you have many stocking options.
the bad is it’s more expensive to get started in a large tank. And there is a lot to learn on how to upkeep a large tank in my opinion.
water parameters is more easy to obtain at start up however maintaining it can be very hard for a beginner. Using fritz complete or turbo start, API products or seachem products all help with getting your water ready for fish. My rule of thumb when starting completely fresh is do not add fish till tank is going thru it’s cycle. If you are more advanced you can add substrate into the new tank from an older established tank and add a sponge filter from another tank add some live plants. And put water treatment of your choice to boost your aquarium cycle. Then wait and test your water than introduce your new fish.
The aquarium hobby is supposed to be fun so remember to make it less stressful especially in the beginning. Do your research first before buying equipment that you might not be able to manage at first. Remember the basics of fish keeping prepare your tank and treat the water and test your water before putting fish in the tank. Waiting a week or two to see if water is cycling is a good way to protect your fish when first introducing them into a brand new tank setup.
learn from others and do your research. It’s taken me 13 years with tiny nano tanks to move up to my first 55 gallon. I learned all my fish keeping by choosing what fish I enjoy and sticking with those fish until I feel I mastered caring for them.
good luck and I hope this basic info helps. Please read forums for more detail on cycling a tank and how to maintain good bacteria in an aquarium. There are excellent videos that Cory has made over the years and I have learned so much about fish keeping thru these videos.
FLNYFish