Sith Droid Mark I: 2d6 - 4hp
Sith Droid Mark II: 2 upgrade slots
Sith Droid Mark III: 2 upgrade slots
Sith Droid Mark IV: 2 upgrade slots
Sith Droid Mark V: 2 upgrade slots
Sith Droid Mark VI: 2 upgrade slots
Sith Droid Mark VII: 2 upgrade slots
Sith Droid Mark VIII: 2 upgrade slots
Sith Droid Mark IX: 2 upgrade slots

(Droids caps at 90-145 (+10/5 per attack upgrade) any upgrades past that can only be used for special equipment).

Free upgrade: masculine or feminine programming.
Combat upgrade increases the droids dice pool by +10/5 to the droids combat rolls.
Armor Upgrade increases the droids hp pool by 1.

Upgrading a droid:
Depending on the kind of upgrade the droid needs various steps needs to be taken, for instance an armour upgrade might need collection or manufacturing of a special material and combat upgrades might need several combat experiences to be stored in the droid's memory modules.

Common droid series:

Sentinel Droid
The most commonly used droid in military operations, they are usually equipped with blaster rifles and sometimes carries personal energy shields. Outward appearance a sentinel droid looks as an armoured humanoid.
Upgrades: 1 combat and 1 armor with each rank

HK-series Droid
Originally of manufactured by Czerka corporation, the Hunter Killer droid series is an assassin droid with extensive programming on how to complete it's given task most efficiently. They appear as a (sinister looking) protocol droid, usually with a very distinct shaped head.
Upgrades: 1 armor every odd rank, rest in combat

Protocol Droid
Not build for combat, protocol droids usually take on a role of an assistant in some area it has been pre-programmed, usually etiquette and translation. The appearance of a protocol droid can vary much from species to species, but the most common appearance is a humanoid protocol droid.
Upgrades: 2 armor with each rank.

Droid miscellaneous Upgrades:

These upgrades all costs the droid either a standard combat or armor upgrade

Cortosis Plating: 
Armor Upgrade 
The droids combat plating is made from refined cortosis. If hit by a lightsaber this will short out the crystal and disable the blade dealing no damage to the droid on a successful defensive action. A disabled blade can be activated again on the wielders next attack action as a part of their attack. 

Personal Energy Shield:
Armor Upgrade
This small devise will generate a small sphere of glowing energy around the droid. It only needs to be activated once to last the whole fight. Once activated it will give the wearer a shield of 5hp, which is damaged first, if those hp are lost the shield cannot be activated again for the rest of the day as it need to recharge. The shield can be deactivated to conserve energy in which case the shield will be refilled in time for the next battle. 

Advanced Evasive Programming:
Armor Upgrade
The droid is programmed with advanced martial evasive actions. The droid can roll twice for defensive actions and select the best result. 

Dark Core:
Armor Upgrade
The power core of the droid is replaced with a Dark Core capable of drawing on the darkside of the force to power and repair the droid. The Dark Core can be used instead of an attack action to repair 1hp.

Advanced Targeting Sensors:
Combat Upgrade
The droid has advanced targeting sensors installed enabling it to better track and calculate opponents. The droid can roll twice on an attack action and select the best result. 

Flame thrower:
Combat Upgrade
Resembling a burly blaster rifle, this weapon shoots out a stream of highly flammable chemical liquid in a cone of 10x10m (approximately 90°), anyone in the area takes damage. 

Sniper rifle:
Combat Upgrade 
This resembles a standard blaster rifle with a longer barrel and usually a scope. If used in combat it can be used to take aim at the opponent and forego an attack action, adding that attack roll as an extra attack roll on the following attack. 

Stealth Field Generator:
Combat Upgrade
This devise makes the character virtually invisible if more than 10m away from the opponent. When used in combat it will add an extra attack roll to the characters next attack action.

Concussion Grenade:
Combat Upgrade
A standard fragmentation grenade, it deals damage to anyone within 5m of the target. 

Flash Grenade:
Combat Upgrade
This grenade is designed to generate a sudden bright light, aiming to blind the opponent. When used, anyone within 5m of the target is blinded and will lose their next attack action.