Is this a good build? Ps: Im very new to building pc.

whats your monitor resoultion

Take a look at the template in the link below, fill it out and post back, that way we can help you better.

http://www.tomshardware.co.uk/forum/353572-13-build-upg...

Approximate purchase date: In about a month
Budget range: $500-650
System usage for most to least important: Gaming
Are you buying a monitor: no
Parts to upgrade:
Do you need to buy OS: no
Preferred websites for parts: newegg
Location: Ho Chi Minh City, Vietnam
Parts Preferences: Core i5 and at least i3
Overclocking: Maybe, im a noob so i don't know much
Your monitor resolution: don't know but maybe you can recommend a monitor because mine is pretty old. So maybe 500-650 for the computer and another 100-200 for monitor.
Additional comments: Prefer to be quiet. Play minecraft, league of legend and want to try new game like battlefield 3 etc.
And most importantly, why are you upgrading: My computer is sooo old that it can only run League of legend and minecraft in very low setting.

1280 x 1024, should i upgrade?

I know this is really hard but please help me lol

This is a nice budget build that leaves you almost $200 dollars for a new monitor if you want one. If you're happy with your current monitor, see the build below.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD Phenom II X4 975 3.6GHz Quad-Core Processor ($82.18 @ SuperBiiz)
Motherboard: Gigabyte GA-78LMT-S2 Micro ATX AM3+ Motherboard ($49.11 @ Outlet PC)
Memory: G.Skill Sniper 8GB (2 x 4GB) DDR3-1600 Memory ($39.98 @ Outlet PC)
Storage: Western Digital Caviar Blue 500GB 3.5" 7200RPM Internal Hard Drive ($58.56 @ Amazon)
Video Card: MSI Radeon HD 7770 1GB Video Card ($113.98 @ Newegg)
Case: Corsair 200R ATX Mid Tower Case ($52.99 @ Microcenter)
Power Supply: Antec High Current Gamer 400W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($45.98 @ Outlet PC)
Optical Drive: Samsung SH-224BB DVD/CD Writer ($17.99 @ Newegg)
Total: $460.77
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-02-15 08:44 EST-0500)

No monitor build

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-3470 3.2GHz Quad-Core Processor ($149.99 @ Microcenter)
Motherboard: MSI B75MA-E33 Micro ATX LGA1155 Motherboard ($59.99 @ Amazon)
Memory: G.Skill Sniper 8GB (2 x 4GB) DDR3-1600 Memory ($39.98 @ Outlet PC)
Storage: Western Digital Caviar Blue 500GB 3.5" 7200RPM Internal Hard Drive ($58.56 @ Amazon)
Video Card: XFX Radeon HD 7850 2GB Video Card ($207.98 @ SuperBiiz)
Case: Zalman Z5 Plus ATX Mid Tower Case ($33.99 @ Newegg)
Power Supply: XFX ProSeries 450W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($57.98 @ Newegg)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer ($18.98 @ Outlet PC)
Total: $627.45
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-02-15 08:48 EST-0500)