As stated above, you should focus most attention of the present, past (passé compose and imparfait are both past tenses and both are commonly used), and future tenses. Why? (1) One can confidently and proficiently speak using only these four tense conjugations and (2) almost all of the other conjugations are based on these conjugations. Take the conditional tense for instance. This tense is formed from the infinitive (parler, manger, dormir, etc.--the verb form with the er, ir, or re ending), with the imparfait past tense endings attached. One should eventually become comfortable with all tenses, including the archaic/literary forms (eg. passé simple), and all of the moods. The imperative mood is quite simple and save for a few irregular verbs, it can be learned in minutes. The subjunctive mood can become rather complex, though you will likely only encounter the present tense in conversation and most writing. In closing, focus your attention on indicative mood, and the present, past, and future tenses. Once you are comfortable and confident with your knowledge of these, learn the conditional tense and become acquainted with various compound tenses like the past perfect and anterior future. Learn commands by studying the imperative, and finally, learn the present tense of the subjunctive mood, and skim over the constructions for other subjunctive mood tenses.
By following these guidelines, you will save time and you will make the learning process significantly easier.