If the requisites for attaining the path of a stream-enterer is to accumulate merits and having favourable conditions, what are the best ways to gain merits and having all the necessary conditions to achieve this?
Ways to earn merits:
Practice the Buddha's teaching.
Practice daily meditation and share the merits with all beings.
Support the Sangha or better yet, become a Bhikkhu/Bhikkhuni.
With every wholesome deed one gets closer to Nibbana.
With every unwholesome deed one gains distance to Nibbana.
Perform the Ten Meritorious Deeds..
4.Reverence or respect.
5.Service in helping others.
6.Sharing merits with others.
7.Rejoicing in the merits of others.
8.Preaching and teaching the Dhamma.
9.Listening to the Dhamma.
10.Straightening one's views.
In addition to that,cultivate the factors for stream entry.
1.Association with people of integrity is a factor for stream-entry.
2.Listening to the true Dhamma is a factor for stream-entry.
3.Appropriate attention is a factor for stream-entry.
4.Practice in accordance with the Dhamma is a factor for stream-entry.
Also here are some things i've observed from personal experiences:
Giving to someone who has greater sila or meditates generally increases one's merit.
Practising metta increases merit (for me).
Giving or performing any good merit towards a noble person increases one's merit substantially.
Accumulation of merit will only give favorable conditions. If you are born and able bodied person and the ability to access the dhamma this purpose is already served. If you miss this opportunity the conditions perhap many not be as favorable again for a long time. So practice hard to achieve the final goal. This effort will not be in vain as if you miss the goal in this life your most likely be in a more favorable position to practice and also your past practice will help with help mastering the teachings and technique easily.