What modds should I do first to a stock Evo x

Go to the Evo X Performance forum. There's a sticky right at the top about this exactly.

And if you don't want to void warranty, talk to your service manager. Most likely you will only be able to do a drop in filter and a catback.

All dealers are different. Ask the dealer you go to if you can do small mods and see if they void your warranty or not. Some will allow some mods and keep your warranty and some dealers will void the warranty if you fart inside the car. lol But every dealer is different. Start with asking them if your scared of losing your warranty before you do anything.

yea there are a few threads you can find where people go over what to do in what order. Simple mods that give best bang for buck are typically ones that will increase airflow and exhaust flow, plus finding a reputable tuner in your area.