Ultimately, a fleet needs to decide if it’s going to operate in a guerilla fashion or in a fortified fashion; there is no in-between.
Guerilla fleets are cheap and expendable though still surprisingly effective. They don’t have as much throughput as fleets sporting pricey high-end ships, but they almost always earn more they they might lose if the entire fleet were to be destroyed.
Fortified Fleets make defense their top priority. The loss of a single ship would likely be devastating, especially if the fleet has not yet earned enough revenue to compensate for the loss and still have enough left over to have made the expedition worthwhile timewise.
In general, only large fleets can be adequately fortified in a manner which makes it worthwhile. Guerilla fleets are sustainable at all sizes, but they inherently have lower throughput than well-coordinated fleets with pricier builds and experienced pilots.
Guerilla vs Fortified Mining Expeditions
In general, guerilla mining expeditions should only use Ventures or its T2 versions the Prospect and Endurance. A single haul in a Venture will pay itself off several times over should the venture get destroyed. The Prospect and Endurance requires a few more hauls before it pays for itself, but once it does it offers substantially better throughput. By contrast, a Mining Barge would require several hauls to pay for itself should it get destroyed.
Compared to the Venture, the Prospect can Covert Cloaked (ie. Cloak AND warp to escape), has better mining yield, and has twice the ore hold than the Venture has. The only disadvantage it has compared with the Venture is a lack of a drone bay and lack of built in +2 warp core strength; however, the benefits by far exceed the disadvantages, especially when a defender is also present in the fleet. If an enemy appears, the first thing you do is activate the cloak, making it nearly impossible for them to prevent your escape. Being 2SWO-capable makes it that much more likely that you will escape to safely. Note that the Venture and the Prospect are the only two ships with bonuses to gas harvesting.
Compared to the Venture, the Endurance has substantially better harvesting yield and three times the ore hold that a Venture has. It also has bonuses to using non-covert Cloaking devices as well as defense bonuses. Basically, the Endurance is the miniature version of a Hulk-Skiff-Mackinaw hybrid: it has the throughput of a Hulk, the defenses of a Skiff, and the ore hold of a Mackinaw scaled down into a 2SWO-capable, substantially more affordable frigate.
The throughput of the Venture, Prospect, and especially the Endurance should not be underestimated! In small mining expeditions, it is usually better to have several Venture/Prospect/Endurances and a few defenders (mostly to ward off rats more so than hostile players) than a few mining barges and many defenders. The reason for this is simple: the mining throughput is going to be roughly the same, but risk for loss and the liability for the loss of any one ship is substantially lower.
Should mining barges be used, the choice mining barge is important in a fleet. The Procurer/Skiff has excellent survivability, but lower throughput than the Covetor/Hulk and a smaller ore hold than a Retriever/Mackinaw; the survivability of the Procurer/Skiff amounts to nothing if it does not have adequate protection in the fleet. The Retriever/Mackinaw is an excellent vessel when mining without support ships (namely an Orca or Miasmos) as it requires substantially fewer visits back to deposit ores. It’s throughput it not as high as a Coveter/Hulk combined with mining support, and it’s not as sturdy as the Procurer/Skiff. The Covetor/Hulk is the ultimate mining barge with unparalleled throughput, but requires mining support (ie. Orca or Miasmos) in order for that throughput to be realized; otherwise, it would have to make so many frequent stops to deposit ores that it’s net throughput would be lower than a Retriever/Mackinaw. In addition to requiring mining support to be effective, the Covetor/Hulk does not have the sturdiness of a Procurer/Skiff. In short, a Procurer/Skiff is always the safest and the best default choice, the Retriever/Mackinaw is a good choice when mining support is limited, and the Covetor/Hulk excels when provided with extensive mining support. When in doubt, don’t fly a barge: fly an expendable Venture, an Covert-Cloaked Prospect, or a 2SWO-capable Endurance.
Guerilla vs Fortified Convoys
Scouting is the best approach to avoiding potential gate camps, though they will not be able to detect the presence of cloaked ships en route. Because of the high value and high vulnerability of transport ships, they often require extensive protection unless the total value of it and its contents is relatively low.
Each of the four empires provide a low-cost, high-defense, relatively high-agility transport that can be used effectively in guerilla convoys. These ships are the Sigil (Amarr), Badger (Caldari), Nereus (Gallente), and Wreathe (Minmatar).
In addition, each of the four empires provide two blockade runners (T2 transport), one of which can use a Covert Cloak and the other of which is heavily rugged.