How do I become a better soldier individually with little to no resources available?

Learn to be a good follower, and take charge when placed in any level of leadership. Set an example for all around you including all ranks. Show initiative, volunteer for the tough jobs; don’t be afraid to share ideas, respectfully speak your mind. Being a good leader isn’t difficult and doesn’t require hours of study. It’s doing what you know is right, all the time....take every opportunity to get your hands on any and all weapons you can. Learn to shoot and maintain them....take every opportunity to deploy for field exercises and make every effort to understand the mission and your units plans. Watch your leaders and learn from them....you can even learn from bad leaders, and from every experience. If you don’t , then you’re not trying to learn. Good luck....the key success is built on small things that add up over time. It’s all really pretty simple....most people make things more difficult than it really is.

Get in better physical shape even if you think you are in shape. Go to the Fort Benning website and look for IBOLC and Ranger school. There are many items you can study there. Ask for Ranger school. Go to Pathfinder. Listen to your NCOs. Ask for mentorship. If you want SF talk to a SF recruiter and try SFRE. Study a for the EIB.
Also like MAJ Chu mentioned there is a lot more to being an infantry PL than being a widow maker. There are also administrative tasks.
https://www.benning.army.mil/

The Army has a good sense of what training and education are needed at each phase of a Soldier’s development. Don’t get too far out over your skis. Learn how to be a good infantryman first. Do all the required training and all of the optional training you can fit in. Two things you should learn a lot about are logistics and communication to be a good officer.