If you haven't done much walking then aim for lightweight gear which is suitable for summer/3 seasons use. It is likely that you will not go walking in winter unless you catch a severe dose of the walking bug. At that point you will have a reason to invest in good winter gear which requires quite a bit more of the hard earned stuff, and you will still use the 3 seasons gear with its lighter weight and other summery attributes at the relevant time.

As for what to buy. Ponchos are great for low wind conditions. They can provide excellent ventilation, cover the pack, removing the need for a rain cover, and in really wet conditions provide sufficient shelter to eat lunch without the sandwiches getting soggy. A poncho can also provide emergency shelter if you get a decent one with tie outs.

A jacket is better for windy conditions and will provide a bit more insulation due to its closer fit but your sandwiches will get soggy. Aim for something that is not too short - one that will cover the crotch and upper legs if possible.

Here, in Australia, I have 3 waterproofs. A heavy Goretex (over 500 grams) which is fairly long - it now gets very little use. A new Marmot Mica jacket (200 grams) for 3 seasons use which I like a lot, and a Six Moons Gatewood cape (310 grams) for multi day walks in more sheltered conditions as I can use it as a waterproof and as a good 3 season tent if I carry a ground sheet, a bivvy or net inner (200g) depending on the expected insect load.
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Mark
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Walking my own walk