Nagtibba trek is best one. You can cover it in one day also! But my opinion is that yiu should go for 2nd day. How to reach? Day 1 Delhi - Dehradun then Dehradun to Pantwari Village via Masoori ( Night stay at Pantwari Village)
Day 2- Start your trek by 9 in the morning and reach to base camp by 3- 4 pm. Night stay in base camp in tents..!
Day 3- Early morning trek to Nagtibba peak from base camp and return back to Pantwari Village by 5 pm .!! Return to Dehradun and then delhi..!!
You can save your day via travelling del. to Ddn in night it.
Approx cost will be 4000/- if. you go with travel company.. !!
Neer garh waterfall is the best place in uttarakhand for summer season.
how to reach there
if you go with your own vehicle then go to rishikesh and then only 30 min distance from rishikesh bus stop to neer garh waterfall
Kunjapuri Devi temple - Sunrise trek(from Rishikesh). I was with a group of 4 along with a guide. This is a down trek from Kunjapuri Devi temple to Tapovan (Rishikesh ). On the way you get to see lush greenery , splendid view of hills, forests and so on. The level of the trek is easy and is suitable for beginners.