One of the most frustrating things about trying to find lightweight clothing and shoes is that the weight is rarely posted with the info about them. Vendor reps rarely know and can't seem to find out the garment weight either.
I usually take a kitchen scale with me when shopping. It's also great for weighing what I already have.
To keep track of the weight you plan to pack (and wear), you can download the pictures from online or take a picture of what you already have. You can edit the picture to add basic information, including weight, right on the picture.
Using those pictures, you can create an album for your potential travel clothes. Creating a 2nd album for specific trips helps to organize the possibles. That album should get smaller as the possibles become definites, or not.
I started all this detailed weighing after seeing the Sarah Murdoch travel talk called Packing Light & Right.
Do you know exactly how much your lightweight backpack weighs? Only by knowing that for sure will you know how much weight you can put in it and still be able to meet your weight limit.
A hand held luggage scale that's in kilos and pounds is great for weighing both the empty and the packed bag. It's also good for weighing things that are too big or awkward to weigh on the kitchen scale.
Looking back to your previous posts, I see that you are going to the Tuscany area in April. Have you checked the weather on timeanddate.com? There you can see the data from past Aprils for many years, not just averages. The link is to April 2019 in Firenze. You can use the drop down box to choose other years. Be sure to scroll down the results. The data is presented in different ways.
I try to not have any pants without pockets. I don't put anything important in the pockets, just things like lipbalm or cough drops or tissues.
These Mountain Hardwear Dynama pants are my latest travel purchase. Pull up, good pockets, big enough to go over long johns if needed, easy wash and quick dry, fun ankle adjustment. At only 8 oz, they will be going to Ireland with me. I get Long ones, 34" inseam. That's as close to leggings as I'll ever get.
Now about the shoes. Shoes are the most important thing to get right, especially if you'll be adding an extra 18+ pounds to your feet at least part of the time. You'll get lots of suggestions. Below are mine.
No matter the weather I wear lace up light boots for hours of walking and standing, just over the ankle or higher.
These high topped Ahnu Montaras are 28 oz for the pair. Sounds like a lot, but weigh the shoes you normally wear to compare. I've worn these or my gray pair in all kinds of weather and over all kinds of terrain for a total of about 15 weeks in Istanbul, Greece, Italy, the UK and Scandinavia.
These ankle high Teva Arrowoods are a bit lighter at 24 oz for the pair. I wore these 5+ weeks in Amsterdam, Portugal and Spain last summer.
These Abeo Adinas are 20 oz for the pair. I'll be taking these to Ireland for 3+ weeks in May. They've been working out well with all my local testing.
Have fun with the shopping, including that in your own closet. And remember that if well coordinated, 3 pairs of pants and 4 tops = 12 outfits. And scarves make easily washed spaghetti sauce shields.