I will assume you are still pretty young, or a recluse of sorts! Whitney is a big first step for seeing the mountains and the country!
It may then be a big shock to see all these strong, ambitious CA hikers in front of you in the permit line. Most people just don't realize what they're getting into, and I'm wondering if this describes you. Do you regularly walk, run, or ski?
I run into complete beginners even here in Northern CA, and am shocked at the stay-at-home mentality that rules so many people! I fear many attempt to break out of their shells, to run into big time trouble. Inexperience is the main cause of mountaineering accidents. Your questions suggest you are not very knowledgable, wondering what hiking boots to get, and even whether to get them.
You'll probably spend thousands to try this peak, and not realizing this is a big serious adventure, even for locals, may see your trip and money all go to waste. I recall running into people trying a hike for the first time, and quickly deciding this is not for them! I felt that way when I started some 37 years ago. However, I was only a tad wet behind the ears, and got serious, started an intense exercise routine, and did Lassen then Half Dome before succeeding on Whitney.
We do have the peaks right here, and you are right to check out opinions from this board. Don't refrain from quoting your stamina and strength, as these are very important in helping people see what level you are at.
If Cancun is on the travel agenda, that seems to be the diametric opposite from something like Whitney. Extreme hiking, then sun and fun on the beach?