A quick example of one possible route:
Summoner
Hit Points
HP at 1st Level. 6 + Con score
HP/level. 1d6 (4) + Con mod
Hit Dice. 1d6 per level
Proficiencies
Armor. None
Weapons. Simple Weapons, Net, Whip
Skills (choose 3). Animal Handling, Arcana, Acrobatics, Deception, History, Insight, Intimidation, Medicine, Nature, Persuasion, Religion, Survival, Sleight of Hand
Summon Servant (1st-Level)
As an action, you summon a creature from another plane of existence and bind it to your service. The Servant appears in an unoccupied space you can see within 60ft of you. The Servant is friendly to you and your companions, and obeys your commands. You determine it's appearance and mannerisms (which has no effect on it's stat block), and choose its creature type; Aberration, Beast, Celestial, Dragon, Elemental, Fey, Fiend, Giant, or Undead.
A servant shares your initiative in combat, but always acts at the end of your turn. It can move and use reactions on it's own, but the only action it will take on it's turn is Dodge, unless you use a bonus action to command it to take a different action. This can be an action in it's stat block, or some other action. If you are Incapacitated or otherwise unable to command it, the servant acts independently to defend you and itself from harm.
A servant vanishes when reduced to 0 hit points, or if you dismiss it as a bonus action. Each time the servant vanishes, it regains all it's hit points and all effects on it end. When you summon a servant, you can summon the same one, or a different one, but you can have only one servant at a time.
Pact Magic (1st Level)
The magic of your bond allows you to cast certain spells while you have a servant summoned. You can't cast spells if your servant is not on the same plane and within 1 mile of you.
You know two cantrips of your choice from the Arcane, Divine, or Primal spell list. You learn a new Cantrip at 4th level, and again at 10th level. All of your cantrips except the first one must be Conjuration, Divination, or Necromancy spells.
Each time you finish a long rest, you choose a number of spells from the Arcane, Divine, or Primal spell list equal to half your level (round up) + your Intelligence, Wisdom, or Charisma modifier (your choice).
Each spell must be of a level equal or lower than your spell slots, and must be a Conjuration, Divination, or Necromancy spell.
You have two 1st-level spell slots, which you regain when you finish a long rest. You can also spend one minute in meditation to recover your spell slots. You can do this twice, and must then finish a long rest to do so again.
At 3rd, 5th, 7th, and 9th level, all of your spell slots increase in level. You gain one additional spell slot at 5th, 7th, 13th, and 17th level (to a maximum of six 5th-level spell slots).
When you cast a spell, you can choose to use your servant's space as the origin, but you must determine line of sight using your own senses.
Summoner's Bond (2nd Level)
You gain one of the following benefits of your choice:
Blood Bond. You and your servant gain proficiency with Light armor, Shields, and with a number of martial weapons of your choice equal to your spellcasting modifier. You can use your Spellcasting ability instead of strength or dexterity for attack and damage rolls with any of the chosen weapons.
Spirit Bond. You gain proficiency with one skill or tool of your choice. Then, choose two of your skill or tool proficiencies. You gain Expertise with both of them.
Mana Bond. Once per turn, when you deal damage with a spell, you can add your Spellcasting ability modifier to the damage roll against one of the spell's targets.
Coordinated Strike (5th-Level)
Your servant can attack twice, instead of once, when you command it to take the Attack action. If you used the Help action on your turn to grant advantage to your servant, it has advantage on both of these attacks.