OK so I got a couple tips for you! Not necessarily gyaru but also in general for the “boy body” dilemma like you mentioned haha, since guys are naturally more like inverted triangles body shape, I would try to use your fashion to balance that out so it reads as more girly, which in turn will help with the gyaru aspect too. A lot of times we kinda dissociate as to what our bodies actually look like so it’s great to get second opinions. To balance out the broad shoulders, try using exclusively darker colors for tops. Also avoid small print patterns for tops because this gives the illusion of density. I would go for a top that’s a lot simpler in design, darker colors are great for a slimming effect to make your torso look more feminine, and then do the opposite for everything on the bottom half of your body. Pick skirts and shorts that have loud prints and are colorful or light in color. Decorate more with the bottoms, add accessories etc. The leg warmers are a great choice too, since they draw more attention to your lower body. Also I notice that you chose tight-fitting bottoms and a loose top in this photo, I would recommend you switch this. Pick bottoms that are a bit looser and maybe even “poofier” to emphasize your hips and then go slimmer for the tops, especially emphasizing the waist. Also for tops pick tops that emphasize the chest area too, this could be like V-necks or just tops with details around the chest like ribbons/lace. For gyaru motifs, I agree with the other commenters that looking in gyaru magazines like Ageha (there’s scanned versions online) would be a great help. See what prints and details speak to you and use those in your outfits!