The overall thrust  of this passage:  Christians must allow trials to accomplish their purpose in "perfecting" faith, thus giving us pure joy. 

Point # 1 Trials test our faith that it might be pure.

Point # 2  The immediate goal of trials is to build our perseverance in the faith.

Point # 3  The ultimate goal of persevering faith is eschatological perfection and completeness – when we will lack nothing.

Point # 4  Christian faithfulness in our approach to trials requires wisdom, which God gives to us generously and without finding fault, if we ask him.