Decided to do a write-up from observation to judge on what starting/possibly final class for MC are viable and rank them accordingly from best to worst:
S Rank:
-Assassin: God tier. Highest attack in the game, can use really strong daggers that are typically easy to access and sneak attack, bows, chakrams, etc. Thieving skills are a bonus so you can free up the rest of your party from that role and take it on yourself. With it as a starting class, you can Counter-Death combo to potentially insta-kill enemies on counter-attacks, and on top of that Assassin gets bare handed proficiency so you can just swing with your fists if you lack better options (and kill instantly with them). Only downside is to get this at start of the game with Counter, you need basically a 40 bonus point buy or higher, or you won't get it due to high minimum stats. Other than that, Alchemy spells are an additional plus.
A Rank:
-Dervish/Spellblade: similar to Assassin but an offensive jack of all trades character that can cast useful spells like Blizzard or use MP for utility Spirit spells. Also gets the Death skill for instant kills, so having this as your starter is a solid choice for the entire game.
-Fighter: MC's default class, and as plain jane as it is, it's one of the better all-rounders in the game. Can use nearly every weapon, equip the heaviest armors, and you get the highest HP gain per level-up, which is insanely important on your main character.
-Lord: Fighter+; this class is designed around tanking and a bit less worldly than the Fighter, but with the Holy magic utility you can help keep the rest of the party alive and protect members that are otherwise vulnerable to many attacks, such as bullying from enemies that want to capture and pin certain heroines. If you take this as a starter you get Counter, which helps you tank and do damage simultaneously.
-Monk: Unlike the heroines, no one's gonna give two shits about you running around in your underwear punching all the baddies, an Monks do respectable damage and stunning per turn. As a starter it's whatever, due to the fact that everything they learn is basically what MC can learn as a Fighter from level 1 anyway (including Counter). Holy magic is w/e cuz you're only using it to heal or damage ghost enemies instead of twiddling your thumbs.
B Rank:
-Thief: Not a great class tbh compared to Assassin, but an extremely vital role to any party cuz of 90% of loot locked behind trapped chests, even enemy drops. You also overlap with Max in the beginning, making this a less stellar starting option, but By taking the role yourself you free up your slot to be filled by literally anything else in the party, including having a heroine take on the fighter role, extra mage, etc.
-Pirate: You're basically a Blacksmith but with some thieving bonuses in your toolset, but you get high HP and decent attack power, which is always nice.
-Summoner: Someone has to take on this role if you're gonna bother with summons at all, and it might as well be you, especially if you can fit the bill from level 1 and start making contracts. Weapon choices aren't really great tbh, especially early on, but your main goal is making contracts so you can summon them later for stronger minions; we all want that awesome Black Dragon, don't lie.
-Priest: A solid frontliner that can equip a few weapons with Medium Range to bonk enemies in row 2 that are hiding behind frontliners, and as a plus side you get plenty of Holy spells to help support your party, and the amazing "instakill Undead" skill, which would be way more useful if the game had more undead (it does not).
-Bishop: A priest with worse armor options but better offensive spells; decent trade off, and some medium ranged staves exist that do high melee damage, so not a terrible choice.
-Bard: Bard's fun. Whether it's very good is a different story, but you can do a few different things, such as acting as party thief, party caster, or supporter. Some instruments do fun things like spell attacks, sleep, giving the Accumulate effect on party members, etc. You are in essence a Thief with spellcasting and a fun mechanic with instruments.
C Rank:
-Smith: If equipment broke more frequently, I'd consider this class to be important, but it doesn't, and you can usually just spend paltry amounts of gold instead. Otherwise you're just a bruiser with limited armor and weapons; just take Fighter.
-Hunter: There's a lot of solid bows, and even more solid candidates for Hunter besides you. Max needs something to do if you replaced him as party thief, so he's better suited for this role tbh. The summoning aspect doesn't do much if you don't have a Summoner making contracts (Gee, wonder which job you should consider taking instead?)
-Druid: Phenomenal class marred by extremely limited equipment. It's a solid bruiser with Alchemy spells to back you up (best utility spells in the game are all Alchemy related), but you'll more than likely prefer the extra options other front liners can provide (or hell, backliners).
-Mage/Sorcerer/Alchemist: Look. Liselle can't change classes, and she's a mandatory Mage in your party. Filling out this role yourself, especially early in the game, means sacrificing your other mandatory party slot to another caster and filling out the rest with non-casters. I'm not saying you can't easily do it, but you're cutting a lot of options from yourself, and in games like this you're better off with just one pure caster and filling out the rest with hybrids and one priest/bishop.
D Rank:
- Valkyrie: The only D rank for the Hero, because he can't be one. Sexist-ass hentai ahh game.