Beginner looking for help deciding on a build

well, i am a long time subscriber and i figured this is where to start, i have next to no expertise in this field, nor does any of my direct family, so i figured i should go here and see if i can get some help. to start i should probably explain my situation first.

i am a Iowan (fort madison, 52627) high schooler whos early 2008 imac had a hard drive failure (from what i can diagnose), rather then fix a machine that couldn't run team fortress 2 on medium, and also just couldn't play portal (from operating system, you can't do much on a 5.8 leopard). so i have been saving for a full custom pc, so far i have 260 dollars, on june 7th i will get an additional 100 from birthday money (and i will turn 16, which means i can upgrade it later with job money)

overall i don't need an incredibly powerful rig, so long as i can play a good variety of games on medium settings i will be fine. i have an aluminum keyboard (that has been through a lot, but i love the swapped Crt and Alt keys), i also have a wireless 4 button mouse, aswell as a graphics tablet (a bamboo one, i cant remember which one, but its the cheapest of the art ones), in terms of monitors i am not entirely sure i can use my hard drive-less mac, but if i can't i could probably find an old one and replace it some other time. 

in terms of an OS, i currently have a copy of mac 5.8, but i don't plan to use it. i have spent enough time with mac and am ready to switch to something else. getting windows 7 will not be a problem for me. i know enough about software that such shouldn't be a problem installing either.

all in all, i thank anyone who can help, this is a field i have never worked in before, but i have been researching this for enough time to be sure i can do it (rather then wait till i have a thousand dollars and buy a pre-build). i am not good at ending these, so i am going to abruptly end it here.

could you say the percise budget? :)

it was in the second paragraph, 260 now, 360 if after june 7th. thanks for replying

Here's an APU system that is close to your proposed budget:

http://pcpartpicker.com/p/3N01B

It should play most games at 720p, some at 1080p.

Ideally, with a budget of $400, you could get an Athlon CPU and a dedicated GPU. It will perform reasonable well in the latest games, whereas the APU will prove to be unsuitable for some.

Here's the base of the build:

http://pcpartpicker.com/p/3MZIN

I've tried to make it as cheap as possible, whilst trying to balance features. So I was little generous with the storage, and I wanted to pick a motherboard with heatsinks. 4GB of RAM will be sufficient to start, you can increase the capacity to 8GB. All it needs is a GPU, priced around $100. 

The 260x is a good place to start:

http://pcpartpicker.com/part/his-video-card-h260xft1gd

It should play a good number of games on medium settings 1080p, including Battlefield 4.

the system looks pretty good (thats more my way of saying i trust you), ill make sure to stalk these parts for sales and get it over time. thanks for the help, i would have never been able to figure out where to start.

If you get the APU system, it is a good place to start. You could add a GPU (e.g R7 265 for $130) later and play a good number of games on the highest settings. That's what I would do.