Explanations/Questions:

This is another arc that for me has had a variety of shapes through several revisions. The smaller units are straightforward enough, the challenge is in how these 'second-tier' arcs then relate to one another:

v.12-13, Don't be surprised at the trial, rather, rejoice

- - - - -

v.14, If you are insulted for the Name, you are blessed

γἀρ (for)

v.15-16, Make sure no one suffers as a criminal, but if as a Christian, glorify God in that Name

ὅτι (for, because)

v.17a, it is time for judgment to begin within God's house

δὲ (and, but)

v.17b-18, if it begins here, those outside in disobedience will not stand

ὥστε (therefore)

v.19, those suffering in accord with God's sovereign design should stake their lives on a faithful Creator.

v.14-16, What relationship does γάρ (v.15) indicate?  There seems to be an atypical role for γάρ here. Most English versions leave it vague in translation. NASB gives it the force of a mild exclamation, "Make sure..." (similar to 1 Cor. 11:22, where it is the forceful, "What!"). See next question...

Is v.14 primarily connected to v.12-13 or v.15-16?  Schreiner (New American Commentary) sees it as a distinct thought added to v.12-13 which together are then Explained (γάρ) in v.15-18. This gives γάρ a strong role in the overall structure of the passage.  My arc however, ties v.14 to v.15-16 under the theme of 'the Name': v.14, ...insulted for the name of Christ; v.16, ...as a Christian; v.16, ...glorify God in that name.

What specifically does v.17a support?  That it is now time for God to be refining his people logically supports a call to joyful alertness (v.12-13), as much as it gives a reason why suffering insult is a sign of blessing (v.14), and probably more than solely supporting unashamed suffering as a Christian rather than as a criminal (v.15-16). 

And is v.17b-18 part of that support or does it add a new point? Though Peter repeats the point from v.17a, he does so in order to introduce an entirely new thought - that those outside the household of God by their disobedience to the gospel are doomed (i.e. What shall come of them?). He reaffirms this point by quoting Proverbs 11:31 (Septuagint).

Is v.19 an inference from v.17-18 or from the whole of 12-18? It is the realities of God's judgment - the refining of his people and the damning of the ungodly - that lead to the imperative to trust in God's sovereign design in suffering and his faithfulness as the author of life. But v.19 also stands as a conclusion to the whole in that his flow of logic has progressed through v.12-18 and culminates with this call to entrust your souls to a faithful Creator.

Summary: Trials should not come as unexpected surprises but as a cause for rejoicing in anticipation of even greater joy  at Christ's appearing.  Moreover, to suffer for the Name is to be blessed and is no cause for shame but an opportunity to honor God in that Name. Indeed, God's judgment begins with his own household. And be assured that that which is aimed to purify his people will be the end of those opposed to the gospel. So as you suffer in accord with God's soveriegn design, stake the whole of your life on the Faithful One who is the Author of life.

Insights:

v.13d, If the participle is not merely providing an additional possibility (...that you may rejoice and be glad) but detailing the manner of the rejoicing (...that you may rejoice being exceedingly glad), then the point of the Ac-Pur argument is that the aim of joyfully expecting suffering in the present is increased and amplified rejoicing at Christ's revelation.

v.17-19, It is the gospel, and the gospel alone which separates mankind. The dividing line is obedience - and what is it to obey the gospel? It is the obedience of faith in which you stake the whole of your life on the faithfulness of the God who has made you.

v.19, "...while doing good."  Peter never leaves righteous living off the table.  Holy conduct does not depend upon the circumstances of our lives.