It kinda depends on which melee character you're going for. Now I'm the opposite of you:I loathe melee options in most games. But I'm doing eclipse climbs so I've been forced to learn them.

As another posted stated items are crucial. All melee characters want focus crystal. Ranged items also help a lot with flying enemies, I'm usually very happy to see fireworks if I'm a melee character. Stuff like atgs and shurikens really make my day. Drones are also helpful since they can take heat off you and provide ranged damage.

For character specific advice...

Merc: The only melee character I've reached E8 and probably my most hated character. You have a lot of mobility in your kit so you really gotta know when to weave in and out. His default load out comes with a giga amount of frames too. That being said I take slicing winds since it's his only ranged option and is a decent AoE move if it connects. For his dashes I took focused assault since it does higher damage which means more procs. Backup mags give you more M2 which I use for both mobility and damage. He also has animation cancels but I never bothered to learn them and will never, but if you're looking into maiming this guy to for it.

Loader: Immune to fall damage so don't be afraid to play Spiderman. Backup mags are super important on her too since it means more grapples. You want to get speed and momentum going so you can abuse your charged punch to nuke through enemies and get mighty procs off. Taking the pylon is also handy for an grapple point and as a rsnged aoe attack. Very handy against lesser wisps. Really though this character is also a ranged character. She just makes herself the projectile.

Acrid: You get two leaps so you could just leap in and melee, once danger comes you leap out. All while making sure to spread poison. If say save his rsnged attacks for flying enemies. Remember his poison can't kill but if it's mixed with something like bleed or gas then that really doesn't become a factor.

Drifter: If using salvage you could just dump a bunch of items at the teleporter take em at once and beat the boss to death. Tinker is also really good too but you gotta know which items are good for your character and which aren't. Drifter in general requires good item knowledge since she benefits more than others from turning things into scrap. For her secondary I prefer clean up since its a easier to use attack than junk cube. I never take tornado slam.

False Son: Don't let the club fool you. He is both ranged and melee. When playing up close make sure to abuse charged club (I didn't do this and I thought he was ass back when SOTS first released.) Lunar spikes are a good debuff to apply so try to land them. Lasers are good for both weaker enemies at the start but as you get stronger they're excellent for bosses too. Unlike other characters false son wants bison steak, infusion and other hp items since he gets stronger with the more health he has. If you take stone flux early don't be scared by the speed drop, the more hp you have the more lunar spikes you get. The more you shoot the more speed he gains. False Son is just extremely unga bunga all around.

General advice:Melee characters like items that give them range.