Glasseslit is currently showing a 30% off new arrival frames promo that requires a promo code, and that code is the lead offer on the page. The 30% off new arrivals code is best when you are buying one or more qualifying new arrival frames and want a straightforward percent off those selected items.
If you are buying a single new arrival frame: use the 30% off new arrival frames code. For example, on a $120 new arrival order the code takes 30% off, so you pay $84 and you save $36 (original $120, percent 30% off, final $84, saving $36). The site also lists a public 30% off new arrivals sale but its terms say it cannot be used with any other offers; the result on a single qualifying item is the same percent off as the code if both apply to that item.
If you are buying two pairs and both are eligible: compare the two codes on the page. The buy one get other 50% off code applies when you buy one selected style and add a second, giving the second pair at half price. For two $100 new arrival pairs the buy one get other 50% off code gives 100 + 50 = $150, a $50 saving (original $200, fixed 50% on second pair, final $150, saving $50). The 30% off new arrivals code applied to both pieces takes 30% off each, so 200 × 0.7 = $140, a $60 saving (original $200, percent 30% off each, final $140, saving $60). In that example the 30% off code saves more than the buy one get other 50% off code.
If your cart is near shipping threshold: free shipping applies on orders over $69. The page says free shipping on orders over $69; use that if your order total reaches the threshold. The offer list does not state whether the $69 threshold is measured before or after a promo code, so bear that in mind when you apply a code.
If you are a first time customer or low spend shopper: signing up for the newsletter may get you special offers and promotions, so it is worth signing up if you expect to receive an introductory email offer. The newsletter is not the main promo on the page and is only appropriate as a low spend or first time customer tactic because no firm discount amount or threshold is stated.
When choosing between offers, run the arithmetic for your exact items. For single new arrival items the 30% off code is the straightforward choice. For multi item carts where one item would be full price and the other half price, compare the buy one get other 50% off outcome with applying 30% off to every eligible item and take whichever gives the lower total. Free shipping on orders over $69 can change which total is lower since the threshold may interact with your final cart total.