Your dissection was actually broke down by what you posted. You basically proved by what you wrote that Knowledge of how a job functions and putting forth the effort to gear it appropriately then using it in practice associates to skill.

My efforts to collect decent equipment for a job I never played contributed very little to the skill I needed to actually play it.
Your "hand me downs" were still collected by you, whether by choice or consequence, but even with these lack of knowledge on how to plan ahead for pitfalls of the job was your down fall. Thus gear alone does not equal skill.

There are many people in game who put in the effort to collect good gear without the knowledge of how to use it.
This is an utter lack of skill by definition since the gear is still useless if you lack the knowledge to apply it in the correct method. Additionally, stating that "transferable skill" equates to skill is inaccurate as not all jobs play the same, especially true when comparing a conventional melee with blu. Knowing how to build a ws set and tp set are not nearly enough to know how to play the job. You would not play blu like you would a thf, you can't play blu like you would a nin, mnk, war, rng, or similar physical DD since melee alone would be insufficient or the passive/job abilities function completely different.

The only comparable job to blu would be rdm as both rely on various sources of damage, has the ability to cure, debuff, and rely on various different sets to gain the utmost effect from the differing gameplay aspects. Unlike other jobs you are far more likely to swap many pieces of gear at once, and a number of times, on these two jobs than you are on conventional melee. This is not transferable skill either, as the spells cast on blu must be set and the blu must learn which are better to set due to limited points and spell slots. Once again, this is typically done in practice or by learning from another source, thus does not translate to lack of effort or knowledge, but instead in an effort to attain knowledge. Hence the hand-in-hand reasoning to equate skill.

Just because a person knows how to play a job, but lacks the gear to play it to its fullest does not make them skilled. Alternatively, just because a person has all the best gear but the lack of how to utilize it also does not make them skilled. The ability to put forth the effort behind why the gear is important, and the knowledge on how to use it in conjunction with the way the job is played equates to skill. If a person knows how to play the job and why certain gear is important but will not put forth an effort to get the gear, they are not skilled due to their own unwillingness to better themselves. This will become exceedingly more apparent when these so called "skilled" but ill equipped users are fighting on the same mob with a fully geared and knowledgeable player due to noticeable gaps in damage from all sources.

Thus skill equates to: Effort to obtain necessary components + knowledge on how to use necessary components to reach peak performance.

You can't have one without the other and still be skilled at what you are doing. This is a concept that encompasses all jobs due to the varied styles of each job. Thus knowing generic information also does not equal skill since it is all encompassing, but is not exact job to job due to the use of different pieces of gear, and building around the different style of play of the jobs.