These are the basic things you should get if you want to AFK fishing overnight (6-8 hours or more), and not get a broken rod or full inventory that halts your fishing when you wake up the next day
1. Balenos Fishing Rod (Upgrade it to atleast +7)
2. Use an Item Brand Spell Stone on your +7 Balenos Rod (can be obtained through the Pearl Item shop or via reward by playing BDO for 2000 hours as an optional reward choice). Branding the equipment will decrease its repair cost by 33%, and the durability consumption by 50%. (what you aim for here is the reduced durability consumption)
3. 63 inventory space atleast, 100+ is best
4. A character below lvl 50 (If want to fish outside of safezone. Above level 50 character is fine and is up to your preference).
Note: Higher fishing rank will slow down your rod durability consumption. Using a branded +7 Balenos Rod on an Apprentice Rank fishing character will be enough to last overnight. Get the character to Skilled Fishing and you wont have to worry about rod durability.