First time budget computer build needs help

I haven't decided about a video card yet, does anyone have any suggestions?

Is the mobo I chose out decent? In the future, if I want to upgrade my CPU or something, will it support it? Is the case/psu adequete?

For that budget go with integrated video, you can always buy a video card later if you want to game (except for potential o'c performance limits mentioned below).

The PSU is junk, get something better even if you have to drop down to 400W in a quality unit to keep cost down (which by the way, might be a higher true wattage capability than a generic psu rated at 580W could provide, they tend to overrate for momentary peak output which is a bit dishonest IMO), there's no way you'll need in excess of 400W for those parts unless you added a higher end gaming video card later, but you don't want something that may fail due to poor capacitors, fan, etc.

One thing about integrated video, it can reduce your ability to use better performing memory timings and frequency which somewhat counters the CPU o'c, but as with a choice to game you can later choose to get a video card for that reason if you wanted to. I haven't tried to o'c G31 boards and can't tell you if the o'c features are as fully supported.

FWIW, I have a E2180 running in IP35-E (great value for what it is) and it was no problem o'c to 3GHz, barely even required raising vcore which is good for you since you seem to be planning to use the stock Intel heatsink which isn't good for too far past 3GHz as higher speeds would require you to start increasing vcore voltage too (and/or more fan noise to do it).

Note that there isn't official support for E2180 in the IP35-E bios yet, some who flashed beta bios had trouble and had to revert back to the earlier final release version (now at V15, IIRC).

As for the case, no idea about it. If it doesn't have good open airways for the front and rear fans you might want to cut out fan holes before building a system into it, or even if the fan hole area is good it would be even better completely cut out - and quieter for any given volume of airflow (or temperature since that board has thermally controlled CPU and system/case fan features).

As for supporting future CPUs, yes IP35-E will but due to the 4 stage CPU voltage regulation it would be a bit limited in extreme overclocking of quad cores. No easy way around that, if you plan to o'c quads a lot you have to recognize it's increasing current which means a more expensive board design to handle that load increase.

I'd have to disagree with another post that assumed you wouldn't be gaming with that budget, if you later wanted to add a decent video card it would do fine gaming, so yes strickly speaking the budget won't cover the gaming card but that CPU @ 3GHz and 2GB memory is a fine start to a budget gaming system, though given a beefy enough video card it'll just increase your need for a little higher wattage PSU.

A better PSU will also tend to be more viable in the future to power your next upgrade by virtue of higher true capacity and longer lifespan.