Short answer

• For fashion-only shopping with frequent, reliable promo codes and brand sales: Zalora. (Zalora.sg)
• For the deepest, occasional price cuts (flash deals, mega sales, huge vouchers) across many brands: Shopee and Lazada during their big sale events (e.g., 3.3, 6.6, 9.9, 11.11, 12.12). (straitstimes.com)

Why (brief)

• Zalora: a dedicated fashion marketplace in Singapore that runs ongoing storewide promos, bank/card partner discounts and app-first codes for new users — so you can often get 10–15% (or more) plus extra cashback and brand-specific markdowns year‑round. Good when you want fashion brands, returns policy and shipping suited to clothing. (Zalora.sg)
• Shopee / Lazada: general marketplaces that run massive flash sales and mega-event vouchers where some fashion items drop to very low prices (sometimes large % off or huge stackable vouchers). Best when you’re willing to hunt timed “shocking deals” or seller vouchers and compare sellers. (straitstimes.com)

Other useful options

• Brand-direct stores (Pomelo, H&M, Uniqlo online, ASOS, Zalando where available): good when a specific brand is running its own sale or you want exact sizing/returns. Check their site/app promos.
• Resale / discount platforms (e.g., Zalora Outlet, marketplace stores on Shopee/Lazada): can yield steep discounts for last-season stock. (rewardpay.com)

How to get the best discounts (practical tips)

1. Time purchases for mega sales (3.3, 6.6, 9.9, 11.11, 12.12) — vouchers and flash deals stack. (straitstimes.com)
2. Use bank/partner promo codes (Zalora often has year‑long card promos). (Zalora.sg)
3. Install apps and sign up as new user (app‑only first‑time codes are common). (singsaver.com.sg)
4. Collect site/seller vouchers and compare the same item across Zalora, Shopee Mall and LazMall before checkout.
5. Factor shipping, returns and cashback — a slightly higher discount may not be better once returns or slow delivery are considered.

If you want, I can:

• Scan current example deals for a few items (e.g., dresses, sneakers, jackets) and show which store is cheapest right now. (This requires a quick look-up.)