The formidable option is to go Vienti (or Blue) Kaulas/Albinosas Leather Shirt+Pants (2 slot, get them to +6 at least) with Lolopanther Leather Gloves+Shoes (2 part set effect for Crit Rate). Optional: go for 15F to get a Lolopanther Medal (better than Max Petamion and has +1 AAR).
Then replace the Gloves and Shoes with the Solmiki version later on, adding in a Solmiki Necklace (Leather) to get the 3 part set effect (lots of stats).
With that setup, you’re building the most amount of C.Rate while including an ever increasing amount of AoE Attack Ratio (which a lot of Archers need) while thoroughly increasing your *defense.
*Legend grade items like Lolopanther and Solmiki have higher base values and enhancement bonuses, at +6, they’re already above and beyond most Lv315 gear def/mdef wise.
Your Shirt+Pants isn’t really a priority replacement when gearing for more potential DPS output. Gem-wise, as an Archer, there isn’t really much you can put on your Glove/Shoe aside from Running Shot Gem and/or Scatter Caltrops Gem.
This setup will also limit the time you’re required to spend inside ET getting geared up (spam 5F until you have shoes and gloves). Going 15F is optional if you’d like to get Lolopanther Medal (necklace), else finish 20F at least once to get your Symbol of G’bb. Spam 25F to get your Solmiki shoes and gloves, then try out higher floors if you’d like (specifically up to 35F to start working on your Solimiki Necklace).
Alternatively, if you’re quite loaded, just buy the Lolo Gloves and Shoes from the market (if they’re on sale).