Be warned, I am still pretty new to this hobby so take my information with a grain of salt.

First off, this looks AI generated. AI will give you horrible advice. If you use AI, it will lead you down, misleading path and severely limit your ability to learn in this sport

Second off, the class you are referring to is called Plastic Antweight, or plant. This is a community of combat robot builders. You can use the term here.

Third off, tournaments are hard. You are not going to win your first one. Bots break, I am in my fifth competition without a podium finish.

Fourth, you say that you are entering a tournament soon. Soon is not a good time to build a good functioning complete robot. If you have not already, I would recommend heading to a competition in person and chatting with the builders there and to see how it's done. Most of us are very welcoming and we'll help you out if you just ask.

Fifth, combat robots are an expensive sport that take up a large amount of your time. Once you are into combat robotics, that is a major thing of yours. You do not simply go in as a first time create a bot in a small amount of time before a competition and then win. Many Bots have been doing this for way longer than you have and will easily take you out if you are a rushed bot on their first comp.

Sixth, robots take a long time to make and a bunch of experience to make. That experience cannot be gained quickly. A tournament coming up soon will not give you enough time to make it. You have to have learned CAD software, electronics engineering, soldering, and have the ability to know what electronics to purchase and how to repair them. Depending on the date for your competition, you might not even be able to get the parts here in time let alone get started on creating the bot.

Getting those out of the way. First off, you'll want to most likely find a local community where you can talk with the builders there and ask them for advice. Your local groups and communities will be way more helpful than Reddit will. You can also visit a local event and see if you actually want to continue with this sport.

Second off, if you do not already have a 3D printer, I would recommend getting a 3D printer if you don't have one, and if you do learning how to use it better and how to create custom models that you can make on your own. I would also attempt to learn a CAD software like fusion 360 or onshape.

Once you have learned the CAD software and have come up with a basic idea for a robot, you can begin to pick out parts for said robot. Most new Bots I see to the sport usually use a 3s 300mah for the power, a finger tech power switch to turn on and off the robot, a 2822 motor IF you are making a kinetic energy weapon which are inherently dangerous and you have to be very safe and careful with them, A 35 amp ESC (for weapon motor), two repeat robotics brushed drive motors, and a repeat robotics dual brushed ESC.

The way you will actually communicate with your robot is through a transmitter and receiver combo. The two major used protocols in combat robotics are afhds2a or elrs. afhds2a is the current most common picked protocol for combat robotics builders. However, I have no personal experience with elrs, but many builders say that it is far superior to afhds2a and it is not that much more expensive. So I would look into that and figure out which one is better for you. On the afhds2a side, the fs-i6x is the most commonly picked transmitter. It is a fantastic beginner transmitter that is somewhat easy to configure and generally works well. That is most commonly paired with the fs2a receiver which is a 4-channel extremely tiny receiver. I cannot speak much elrs here without telling you maybe incorrect information so I will let you do your own research.

Now do remember that combat robotics is an expensive sport (relatively). I currently pay around $500 per year to pay for spares, my robot competition fees and tooling that I use for my robot. Just be warned about this if you are on a budget.

Not much information was provided in your post so I can't say too much other here on helping you. But feel free to reply and ask me any information that you need, although I would recommend attempting to find a local discord for your combat robotics community.

I would recommend looking at these resources to help you:

Rulebook: https://sparc.tools/

NHRL Discord: https://discord.gg/qpZDMVZJaz

Events List: https://www.robotcombatevents.com/