Buying a budget smartphone today is better than ever before. You have good Symbian smartphones like the Nokia C5-03 of E6 being sold for just a bit over Php8,000. There are Samsung Bada phones being sold at the same price point. There is actually a RIM BlackBerry phone, the 8520 being sold for under 10K. Smartphones have gotten cheaper.
I think Nokia's Symbian OS is really on its way out, so I would avoid one of those. All the talk of continued Nokia support for Symbian is just to convince you to buy one until they move on to Windows Phone 7. Samsung's Bada, never really went anywhere in the first place, I do not see the point of getting one now. There are no Apple or Windows Phones 7 devices being offered at there price points, so what do we have left.
If you use BlackBerry services, and need a new one, I would recommend the BlackBerry Pearl 3G which can be had a Php9,950 with a two year warranty or BlackBerry Curve 3G available at Php12,450 with a two year warranty. If you have a bigger budget what not get a Pearl or Curve 3G, and a BlackBerry Playbook, rather than a more expensive BlackBerry phone. The QNX OS, on the PlayBook is BlackBerry's future.
A BlackBerry is a good way to stay connected with the Php300 a month BlackBerry Push-Mail or Social packages being offered, by all carriers.
On the Android, front, you want to find a phone that is running Android's 2.2 OS or higher with a capacitative screen, and a resolution of 320 x 480 or better. Why? Android's 2.2 will allow you to install apps on the SD card. Android 2.1 and older install apps on the internal storage. Budget Androids have small amounts of internal storage.
Capacitative screens require a light touch to interact with it. Resistive screens actually require applying pressure to the screen. Resistive screen do work, but capacitative screens are much more comfortable to use.
As for the screen resolution the 320 x 480, that was Android's original screen resolution, so it gives good (but not 100%) app compatibility. We used to recommend even Android with 240 x 320 screens awhile back, but that it when phones with 320 x 480 screens were expensive.
Given out criteria, what looks good in the Android world. The LG Optimus One is a solid choice with Android 2.2, a 3.2-inch 320 x 480 capacitative screen available at now just Php9,800 with an official warranty. It is getting old, having been released in the 4th quarter of 2010, but price reductions continue to make it a good choice.
Another option would the the Alcatel OT-990. Specifications are similar to the LG Optimus One, but it has a larger 3.5-inch 320 x 480 screen. The OT-990 is priced a supposedly 15K (are they crazy) but is available at a promo price of Php9,999. I think this phone will be on "promo" for its entire life. The LG Optimus One is a tried and tested product, making it easier to recommend. The larger screen might be worth taking a "risk" on the Alcatel OT-990. Pick your own poison.
At about Php13,250 you will find the Samsung Galaxy Ace. The Galaxy Ace is a bit faster the the Optimus One, but I don't think a user would actually notice. What makes the addition 3.5K worthwhile is the 3.5-inch 320 x 480 screen and the camera which is much better than one found in the LG Optimus One. Actually the Galaxy Ace has a very good camera.