The correct choice is 'ように' (forming '撮れるようになりました' - became able to take / developed a state where I can take). The grammar pattern '[Potential/Non-volitional Verb] + ようになる' expresses a gradual change in state or ability over time. Sentence context: '...gradually I became able to take photos beautifully.' 'ために' is used only with active volitional verbs, and potential verbs like '撮れる' do not match 'ために' for expressing state change.