IMHO, you can't improve what you can't measure.
The easy first steps are to accurately measure your water quantity, water temperature, grist mass (dead simple), and mash ph. This means you need calibrated vessels and thermometers and a ph meter. The other "instrument" that I would say that you shouldn't do without if you want to learn about mashing and what the enzymes are doing (the whole purpose after all) is a bit of iodine and an eye dropper. -The iodine from the pharmacy will work. Simply pull a tiny bit of your mash liquid and drop a single drop of iodine into it and observe the color -dark black indicates the presence of a lot of unconverted starch and high molecular weight carbs; as the mash continues this will turn bluish to redish, and eventually will result in basically no color change at all (just iodine dissipating).
-YES temp determines how fermentable your mash is, but the enzymatic power of your mash (the enzymatic power of each malt averaged out based upon the % contribution of each malt in the grist) determines HOW LONG the mash requires to convert (temperature also impacts the speed of conversion). You can actually SEE / MEASURE where conversion is with a simple eye dropper full of iodine. WARNING: Iodine is poison; throw away the part that you test.
If you get a refractometer to keep track of your extract you can simple test each sample for gravity AND starch conversion if you have iodine on hand.
Getting your water into an acceptable range for brewing is important but pre-boiling your water with a campden tablet is dead simple and will get most waters into an acceptable range. The most simple way to get your mash into the right ph range is to test the mash directly (after cooling a sample) and then adding calculated amounts of lactic acid, stirr, wait 4 min and test again. -You'll figure out roughly where your ph typically ends up for light and dark beers pretty quickly.
Also make sure your mash thickness is at an acceptable range (2.5 liters of water per kilo of grain - 3.0 liters per kilo is a great place for most beers and most equipment.)
You want to avoid problems during sparging so again a calibrated ph meter and thermometer are important; batch sparging is simple, possible with any equipment, and less likely to result in extracting tannins/polyphenols. (So start out with batch sparging and you can worry about other methods far in the future (or never, as other methods won't make better beer, they'll just increase your efficiency) after you've got sanitization, yeast, and fermentation down.)
Once you have some experience with your system and have these things dialed in, then you can focus on more advanced water chemistry and adapting your mashing process for your materials (assuming your system supports it). -The single best resource I know for this is the book "New Brewing Lager". Some higher protein malts and wheat beers generally benefit from a protein rest and different temperature rests for different periods of time. -New Brewing Lager will help you to understand what malts / grists will benefit from the more advanced multi step mashes.
If you decide to go crazy and try traditional decoction mashes (with appropriate low modified floor malts that are not available from SOME suppliers), New Brewing Lager will give you the information to do it, assuming you have the equipment necessary to boil the decocted portion separately.
Eventually you can go nuts with highly accurate Pt100 temp probes connected to PID logic controllers with enhanced "fuzzy logic" and possibly RIMS/HERMS equipment to ensure that you always mash at the right temp at the right time, but these things are unnecessary; if you have the right equipment and know your system you can hit the right temps for the right amount of time, too. (A simple keggle can enable you to brew everything; a cooler box mashtun is better suited to infusion mashing but if you go crazy enough with the equipment you can adjust any system to do multi step mashing (RIMS, HERMS, Steam-injection crazy time).)
IMHO, worrying about water chemistry too much early on is focusing on the wrong thing. Start with water that tastes good and is in the acceptible range (1/2 campden + pre-boil) and adjust the ph with lactic acid if necessary; that's ALL. -Add 1 tsp of calcium chloride for malty beers and 1 tsp of gypsum for hoppy beers; 1/2 tsp each for malty and hoppy beers and call water chemistry "good enough" until you get the rest nailed down. (Too many people waste far too many hours on esoteric incredibly minor tweaks to water and ignore some really big items that could dramatically improve their beers.) -On that subject, once you have the basics of not screwing up during mashing down, it's probably better to focus on sanitization, yeast health, and temperature control to make your beer better; then come back to mashing and increase your knowledge and experience there.
Adam