Short answer — it depends on what you want:

• Zalora — best for fashion-focused, brand-name sales and big seasonal markdowns (ZALORA runs fashion events with sitewide vouchers and promos up to ~80–90% during big sales). (zalora.com.ph)
• SHEIN — best for the lowest-priced fast‑fashion / trend pieces and many stackable app coupons for first‑time and repeat buyers. Good if you want very cheap basics and lots of promo codes. (philstar.com)
• Shopee and Lazada — best for platform-wide voucher stacking, hourly/flash deals and huge marketplace sales (3.3, 9.9, 11.11, 12.12) where many fashion brands and sellers offer steep discounts and bank/payment promos. Use these when you want big discounts across many brands or extra voucher stacking. (coupons.rappler.com)

Quick tips to get the best discounts

• Time purchases for major sale events (3.3, 9.9, 11.11, 12.12 and mid‑year/seasonal sales). (zalora.com.ph)
• Stack vouchers + payment/bank promos and app‑only codes (platforms and sites commonly allow stacking during big events). (gadgetmatch.com)
• Compare the final price (item price + shipping + returns policy) — a low sticker price can be wiped out by high shipping or return cost; Zalora, for example, advertises free shipping and easy returns during promos. (zalora.com.ph)

If you tell me what kind of fashion (designer/brands, fast‑fashion, shoes, sportswear) or your typical budget, I can recommend the single best place and current promo hacks for the Philippines.