Hi there Mr. Thunder! Welcome to the PC and the world of competitive battling! :D
If you're going to be successful, you're going to need a full understanding of EVs, IVs, and Natures. These things must be applied to your Pokemon if you want to excel in competitive battling. These things are essencial to anything and everything competitive related and your team will lose unconditionally without them. Let's face it, Breeding for perfect Natures and IVs and EV training is very, very time consuming. But if you want to have a successful future in competitive battling, you need to understand and apply these things.
However. If you want the instant gratification of competitive battling without all the stress and time commitment of training/breeding, I highly suggest you download Pokemon Online. Pokemon Online is a real time competitive battling simulator and an excellent Wifi substitute. You're able to choose your Pokemon and insert all the EVs/IVs/everything with a click of a button as opposed to actually training your Pokemon. That being said, you do still need a deep understanding of the science behind EVs/IVs for each Pokemon to use it properly.
I know you used the term "reasonable", but I'm going to assume that means, "not losing constantly", so that's what my responses are based on. So, I answer your question with a yes and no.
Can you be a successful battler without a full understanding of the EV/IV processes? No. In all aspect of competitive battling, you will find yourself using the knowledge of a Pokemon's attributes to win.
Will you be able to be successful with partial investment? No. Competitive battling is very serious. If you expect to do well, you need to be committed to doing the work. If the work is an issue, than use Pokemon Online. There is no way to "50%" your team and expect to win, but there are shortcuts to get to that end result.
Can you battle competitively without training a team? Yes. With Pokemon Online.
If you need a guide on EV training or Breeding, just ask! :) We can find links to guides for you to read here, or you can post your questions in the Q&A Sticky at the top of the forum. Once you have a team set up, just come back and post an RMT so the raters here can help your team be as prepared for competitive battling as it can!
Good luck to you!