its a giant balancing act between 3 factors
light, nutrient availability, and carbon availability
if any of those 3 are out of balance, it creates problems
low tech is easier to start since it requires the lowest amounts of the 3 elements
high tech is fun because you can grow basically anything, but its the hardest because if any of the 3 areas start to slack, your tank is going to quickly get problems and take a while to fix up
biggest thing though, is know what your goal with your tank is before you set it up, know if you want to be low-tech or whatever, know roughly where you want to take the tank look wise, and make a plan. Planted tanks that are rushed together with little thought are not satisfying and quite frankly, tend to suck and become a giant pain to make into something you are happy with. do it right the first time, ya know?