I heard someone say the best kind of seva is Simran. Otherwise, how do you think the best types of seva are for the Panth.

Yashdeep Ji according to Gurbani
ਸਾ ਸੇਵਾ ਕੀਤੀ ਸਫਲ ਹੈ ਜਿਤੁ ਸਤਿਗੁਰ ਕਾ ਮਨੁ ਮੰਨੇ ॥ ਜਾ ਸਤਿਗੁਰ ਕਾ ਮਨੁ ਮੰਨਿਆ ਤਾ ਪਾਪ ਕਸੰਮਲ ਭੰਨੇ ॥ AGGS 314
Sa Seva Kiti Safal Hai Jit Satgur Ka Mann Mannae || Ja Satgur Ka Mann Mania Ta Pap Kasanmal Bhanae ||
ਉਪਦੇਸੁ ਜਿ ਦਿਤਾ ਸਤਿਗੁਰੂ ਸੋ ਸੁਣਿਆ ਸਿਖੀ ਕੰਨੇ ॥ ਜਿਨ ਸਤਿਗੁਰ ਕਾ ਭਾਣਾ ਮੰਨਿਆ ਤਿਨ ਚੜੀ ਚਵਗਣਿ ਵੰਨੇ ॥
Updes J Dita Satguru So Sunia Sikhi Kanne || Jin Satgur Ka Bhana Mannia Tin Charri Chavagan Vannae ||
ਇਹ ਚਾਲ ਨਿਰਾਲੀ ਗੁਰਮੁਖੀ ਗੁਰ ਦੀਖਿਆ ਸੁਣਿ ਮਨੁ ਭਿੰਨੇ ॥੨੫॥
Eh Chal Nirali Gurmukhi Gur Dikhia Sunn Mann Bhinnae ||25||
Fruitful and rewarding is that service, which is pleasing to the Guru’s Mind (Teachings). When the Mind of the True Guru is pleased, then sins and misdeeds run away. The Sikhs listen to the Teachings imparted by the True Guru. Those who surrender to the True Guru’s Will are totally imbued with the Virtues of the God. This is the unique and distinct life-style of the Gurmukhs: listening to the Guru’s Teachings, their minds blossom forth.

Seva is one of the five virtues in Gurmat. Seva of Tan, Mann and Dhan should be performed without ego according to the spiritual teachings of the Guru (Above Shabd). Seva should not only be at the institutional level but every activity of daily life should be an act of Seva. Philanthropy should be done where needed, not just an act of giving at institutional level. Everything is a manifestation of the truth, and our very lives become an affirmation of that. Even if we do not pray every day, and cannot visit Gurdwara as often as we would like, keep the Guru’s Virtues in mind and perform the best we can. Because those things that keep us busy: job, families, love of sports, passions, hobbies, friends, music, we should pursue to excellence, to the fullest of our abilities, and with Waheguru (Virtues of the God) in our mind. They are all part of the holy life we lead. Help those in your vicinity we will be touching the Divine.