For mining to cash in gil keep and eye on all of the shards and stones like on my server the shards vary day by day and earth and water was the highest but it changes.. An always check the market board for any hearted items.. As well as what crafters need for the new crafts.. Another thing I did while leveling miner get a stack of 99 of the new stuff you get the most exp on while getting the shards as I get the gp back to gather more on the +gathering node..
And there is also doing duns as you level your fighting class because each mob drops so many gil ..
Another tip I got try to do your challenges every week where it gives a good 1 or 2 k for a challenge completed and most of them are pretty easy and things you would do regardless
Best of luck
Oh last thing for the boring grind of shard mining put on a movie and do both makes the time flow an things not as horridly bad