for me you need the absolute basics, stuff you can control and that's 2 things
1. water
2. beans
i put water first because like 90% of what you're drinking is water anyway, so have good water, now you don't have to pour evian down the coffee machine everytime you make something, a cheap brita pitcher for 15 bucks will turn tap water into, good enough.
what these filters do is just remove a bit of clorine and particulates, i mean you get your water from pipes that are 10s or 20s or maybe even 100 years old, you're gonna have particulates in there.
a simple
HM Digital TDS-EZ Water Quality TDS Tester, 0-9990 ppm Measurement Range, 1 ppm Resolution, +/- 3% Readout Accuracy - Amazon.com
will tell you how much particulates you got, heck if your tap water tastes metallic, or your hair after a shower is a big lump (your wives/gf's will be the first to tell you the water sucks) at least you'll know that much. (i.e. hard water)
when i travel, i make my coffee with water bottles tho. (it's just easier)
beans... you know imo as long as they are whole beans and in those airtight bags (not the paper mache kind) with that little plastic knob at the top (all bagged coffees that are airtight sealed have this, this is so that co2 gases can escape the bag, and not burst the bag after a few months storage i think, plus less co2 gassey taste i guess) it's all good.
again i said whole bean, preground is shit, you can't treat coffee like day old refidgerated pizza, when you make coffee, you gotta have whole beans and grind them minutes before brew, the instant a bean is ground, it's on a timer of death.
so to make my life easy when i travel my coffee pack is usually
1 aeropress
1 hario mini (it fits right inside the aeropress)
paper filters (i'm not really a paper snob, and i actually hate sludge and grinds in my coffee)
i'll buy bottled water (or a jug) at the destination grocerystore and see if there's a big supermarket that carries whole bean bagged coffee. (or really, i could just buy my own unopened bag and take it with me, if i know the destination and some places really don't care whole beans, they'll always have ground tho)
after that it's all manual stuff for me at home.
i don't take milk with my coffee (it's black or a tiny bit of cream for me) but if a friend comes over, i have milk or parmalot around. i don't have an espresso machine any more (tired of the tamping, knocking... blah blah) so if they want frothed milk, i'll put the milk in my bodum french press, microwave it put the cover on and pump it up and down for like 30s, get's pretty frothy.
(i use the french press for frothing, brewing/serving tea and if some oddball wants french pressed coffee, it's there, it's pretty versatile)
i mean thats half the cost of those high end pro-sumer espresso machines anyway, they have double boilers and shit just so you can steam milk at the same time
otherwise you can just get this
Capresso frothPRO : Amazon.com : Kitchen Dining
and it'll froth and heat up your milk for you, unattended, those froth wands (bodum has a wand attachment also) require attention and holding a button, the capresso doesn't.
and for a grinder i just use the bigger hario with a nut and hand drill mod, you don't "need" a 500 dollar grinder, it does look better than a hario attached to a hand drill tho, ha.
aeropress/melitta/hario60 (sometimes the moka) is what i use at home, no big crazy machines anymore. actually i stayed at a marriott got used to the cheap ass 15$ mr coffee, it dripped pretty well and it just had 1 button, on/off, and the way it drips/percolates it kind of blooms the grinds pretty well, i saw passed by it while i was blackfriday shopping and just got it, it works nice... altho the brewing temp isn't ideal. it's at 170f, it really should be 200f (snobs say 202f, fucking christ), so i just put in half room temp water and half already boiled kettle water, comes out 190ish.
i think i'll get an espresso machine again soon, i think imo as long as it's a pump (not steam, pump = more bar pressure but of course costs more)
i'm thinking about this
De Dining
the most entry level pump around, reviews are good, it is of course not fancy, it's not even a single boiler, it uses a thermo block (or coils) pretty sure the basket is pressurized, my grinds are good enough that i won't need the pressurized basket, and i think you can mod it out.
coffee imo is about control, with that i have a basic digital scale, heck you should have one anyone if you cook for measurement and if you're a baker, necessity (i think mine is one for mail, it's pretty old)
a water tester
and a temp gun, to measure heat. (i actually need a real temp gun, i'm just using some radio shack gun my wife had lying around and it maxes out at 200, it says high, ha)