"Cheap Filters make 'expensive' lenses 'cheap'" - Sorry - BIT of a gear-grinder that one; small counter-thought to the notion:-
A 'Cheap' CPL might cost about a fiver. It's a single (flat) optical 'element', that blocks light, it doesn't bend it, housed in a simple metal bezel. It is not exactly the most intricate bit of optical equipment to manufacture, and there is only limited opportunity for 'lack' of quality control in the product to introduce significant 'image degradation'.
For comparison, a typical 18-55 kit lens is a much more complex and intricate device with far more opportunity for lack of quality control to diminish IQ, yet with eleven or so optical elements individually offering far greater opportunity to diminish IQ, before they are assembled into the body where with movements and mechanics even more opportunity for lack of QC to diminish potential IQ, in a lens that retails for under £100? each precision ground element is probably made down to a price and standard lower than even a 'cheap' CPL?
And THEN... in use, where keeping your kit clean, and using it appropriately is far more influential than the quality of the kit itself? AND where the optical standard of your kit, has such tiny influence over the ' standard' of your photo's, and you are far more likely to cock up a shot from poor composition, or lack of subject interest, than having that extra 'nth of precision in the hard-ware?
There is 'truth' in the suggestion, and I have a couple of old cheaper polariser filters from way-back when, that really DO diminish IQ; one of them ISTR gave a rather nasty blue-hue particularly on slide film, but these days? 'acceptable quality levels' have tended to push all into the middle ground and the differences between 'cheap' and 'expensive' are usually that much smaller, in an arena where 'significance' is diminishing anyway.
IMO it's just not really such a big deal, and IF you use filters, you aught to accept that there is always going to be a loss of some-sort for any gain you hope to achieve.
OP: keep it clean, keep it scratch free, and be careful of 'technique' - a filter in-front of the front element inherently offers opportunity for 'flare' either from incident light raking across flat front of filter, or internal reflection between filter and lenses front element; curve of lenses own front element plus any 'hooding' provided by the lens body even without accessory hood, would tend to help control this without a filter, so if you use an accessory filter it's something to be wary of. But otherwise?
Yeah, out-doors I tend to use CPL pretty extensively on 'normal' & 'telephoto' lenses. My favourite subject is custom & classic motorbikes though, which frequently have a lot of 'bright-work' in chrome and shiny paint, and a CPL can remove a lot of unwanted reflections and hot-spots in that situation; for landscapes and other out-door shots? Most noticeable effect is probably boosting skies and saturating colour, but can still cut out a lot of distracting reflections or glare, most noticeable over water, where you may actually not want a CPL to retain dancing highlights and 'texture' in the surface of a lake or pond or similar.
While polariser used for max effect can drop exposure two or three stops, which in strong sun-light may be an advantage, but as light levels dim can become a disadvantage; and give dilemma for evening/sunset shots, when low raking light is providing more 'glare' and 'reflections' you might want to control with a CPL, but lower light levels beg you not using one to keep ISO down, the aperture tight or shutter up.
As ever, so much more is in the technique, not the technology; so practice practice, practice..
