Actually, the opposite is better - reset as soon as you can. You will get fewer shares, but you will be able to do many resets in the time it took you to do just one for 1.4M shares, so you will gain more shares. This assumes that you are willing to sit at your computer and keep pressing buttons. If you plan to step away then it obviously makes sense to let the game grind in the meantime.
And spending gems on double shares is a terrible waste. You can get as many shares as you want by keeping resetting (they soon become fairly useless anyway since the decorations grow exponentially in price - right now mine are over 100M for another level). Save your gems and spend them on the multiplier in the shop.