Not all engineering blueprints or experimentals in Elite: Dangerous are worth the cost. This will be a brief overview of the GENERAL good engineering choices. It will list a few choices, but will NOT cover every possibility.
Use it as a guideline or starting point for your builds, and adjust as you like.
Core Internals
Hull
Combat/Safety: Military; Heavy Duty + Deep Plate. Reactive is not worth the cost.
Other: Lightweight; Heavy Duty + Deep Plate. This engineering adds zero mass to lightweight hull which is already zero mass.
Power Plant
ALWAYS A-rate your PP.
Armored + Thermal Spread. If you want to run cooler, use Low Emissions but you may need to size up the plant. If you need more power, use the Monstered experimental and only go to the Overcharged blueprint if you really need it.
Thrusters
A-rated, Dirty + Drag Drives. Clean is a trap with very few actual uses. Stripped Down is not worth the tiny range increase.
Frame Shift Drive
A-rated, Increased Range + Mass Manager. Deep Charge technically gives a little more single-jump range on size 4 FSDs and below, but the increased fuel usage and reduction in total range isn’t worth it. Fast Boot does not decrease charge time.
Life Support
Lightweight. Choose your rating according to your threat model: if your canopy is going to get shot out, you may want better rated life support.
Power Distributor
A-rated for combat and mining, D-rated for everything else. Engineer Charge Enhanced + Super Conduits. Recharge rate is far more important than up-front capacity.
Explorers have the option of significantly downsizing their PD while engineering it Engine Focused + Super Conduits (or Cluster Capacitors) to keep one boost in normal space.
Miners have the rarely needed option of going Weapon Focused + Super Conduits to drain a rock even faster. Make sure your collectors can keep up.
Sensors
Combat: D-rated, Long-Range. The extra range from A-rated is usually not needed.
Others: D-rated, Lightweight.
Utility Mounts
Shield Boosters
Combat: A mix of A-rated Resistance Augmented + Super Capacitors and Heavy Duty + Super Capacitors. Downrating is a way to balance shield strength and power draw.
Explorers: E-rated, Heavy Duty + Super Capacitors is very powerful.
Chaff
Ammo Capacity
Heatsinks
Ammo Capacity
Point Defense
Ammo Capacity
Kill Warrant Scanner
Fast Scan. Bind to the same fire group as your lasers.
Frame Shift Wake Scanner
Long Range or Fast Scan
Optional Internal
Shields
Combat, Bi-Weave: Thermal Resistant + Fast Charge; if your distro is the same size or smaller than your shield, use Lo-Draw instead.
Prismatic/Normal: Reinforced + High Capacity. If this is a combat build then make a couple boosters Thermal Resistant.
Shield Cell Bank
A- or B-rated. B-rated gives slightly more total megajoules.
PvE: Specialized + Boss Cells
PvP: Rapid Charge + Recycling Cell
Hull Reinforcement
Heavy Duty + Deep Plate. If you’ve gone Reactive hull, put Thermal Resistant on the smallest HRP.
Limpet Controllers
Lightweight
FSD Interdictor
Expanded Capture Arc
Detailed Surface Scanner
Expanded Probe Scanning Radius
Auto Field-Maintenance Unit, Fuel Scoop, Refinery
None.
Weapons
Weapons have a lot more good choices. See the PvE Guide for more in-depth discussion. These are good starting points, not the only viable choices.
Lasers
Long-Range + Oversized. One Emissive. A beam or two with Long-Range (not Efficient!) and Thermal Vent is good if you need heat control.
Used fixed lasers if you can aim, gimbaled if not.
Multicannons
Overcharged + Incendiary. One small with High Capacity + Corrosive.
Use gimbaled multicannons by default, especially if you are mixing weapons with different shot speeds.
Rail Guns
Long-Range + Plasma Slug
Plasma Accelerators
Efficient + Plasma Slug
Fragment Cannon
Overcharged + Incendiary. One with High Capacity + Corrosive.