Blue/White Rarity AL Ship Recommendations

List of blue and white rarity ships worth keeping.

Ships with retrofits get massive buffs later in the game. Using them now will prepare their retrofit requirements.
Ships without retrofits are good immediately and will stay at around the same power.

Destroyers:

Kagerou - High torpedo damage, frontline torpedo buff, gets retrofit later on. Highly recommended.
Fortune - Makes your backline tankier, decent damage, starts with a retrofit.
Fletcher - Buffs other Fletcher class, serviceable on her own.
Cassin and Downes - Their retrofits give them excellent survivability.
Comet, Cygnet, Crescent - Decent statlines. All three get a retrofit.
Shiranui - Budget torpedo nuker. Gets a retrofit that makes her very powerful.

Light Cruisers:
Phoenix - Gunboat, amazing self-heal skill. Highly recommended.
Leander - Gets a great support skill set from her retrofit and good stats. Highly recommended.
Ajax and Achilles - High damage, get retrofit later on.
Brooklyn - Gunboat, buffs other gunboats.

Heavy Cruisers:
Portland - Decent damage, her retrofit makes her a monster tank. Highly recommended.
Chicago - Decent gunboat.
Suffolk - Starts with a retrofit, good damage.

Carriers:
Shouhou - Heals your frontline a lot. Gets a retrofit.
Ranger - Her retrofit gives her a very high, but very random damage cap.

Battleships:
Pennsylvania - Has a good barrage skill to screen clear.
Nevada and Oklahoma - Low cost battleships, their retrofits make them quite good.

Keep any ship you personally like as well.

If you'd like to know how to use these ships and more, check out this tier guide by Kawaii Five-O: https://pastebin.com/ZMBi8g6R