Suggestions for charts to download.

Navionics app, every time. By far the best available.

Only downside is if you want to overlay WiFi instruments on it in which case you’ll want to use something like the far clunkier iNavX.

I believe you’re in Spanish waters. Navionics’ Boating Europe app covers from you right through to the Black Sea and right up to Northern Finland for £38 (or let me guess, less if you’re not buying from the UK?!). Just not the UK, but that’s Brexit for you!

You download the parts of the area you want to be able to access offline, depending on the memory capacity of your iPad.
 
Navionics charts work well on my ipad at £59 each. Not as naval as chart plotter as does not have range circles or grid lines but a very clear display and the plus version shows daily tidal stream. Only trouble is coverage of Europe chart at £59 leaves West of England out so I needed 2 charts from Cornwall to Brittany.
 
I know you said iPad.............but.......there are alternatives which may be of interest to the OP and others.

My boat electronics uses Navionics so I bought a Tablet more out of interest than need. I went for a Lenovo Android / visitmyharbour / Marine Navigator app with UK Raster charts.

Pretty basic but functional, really cheap, incredible battery life, lousy sun screen viewing. I went this route because I like the familiarity of Raster charts and membership of VMH gives a lot of UK coastal harbour and anchorage plans. Vector charts require an extra dimension of use, zooming/checking the layers to ensure that there are no hidden hazards on your rhumb line.
 
Recently down loaded Navionics UK and Holland HD version for android (includes Ireland BTW), seems pretty good. €59.99
 
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