Alright, here's a more compehsive version.
Goal - Get the FINAL hit on the big jungle camps which have a red minimap icon. Note - it is not always the big grevil, but the last one alive. So - you're level one, you opened your stocking and you found a set of boots. These boots will either be one of the standard 6 pairs or iceskates (100MS with better traction on the ice-rink that is now the river - only applies in human form).
you have 2 forms - grevil form with 2/3 spells and passives, no mana - but your spells run off cooldowns and standard char form. Grevil form has higher stats than human form - BE AWARE OF THIS, IT WILL SAVE YOU. Some heroes will need to make the most of this (mostly disablers). you have 2 health bars - human form and grevil form and morphing with the pipe takes 2 seconds and switches between them - this will save you, often.
So for example, we are 1 minute into the game and I'm Sven (because lets face it - Level 1 AoE stun rips people). I stay in human form until the inevitable first fight starts, land a stun then BAM - i start on my pipe and transfer to grevil form and start killing people.
OK - so we had the inevitable level 1 fight and now it's pittering out and it's onto the camps. These camps are TOUGH - do not solo them. you will probably fight over them with the enemy but remember - last hit is all that matters so dont wory if they get there first. lets pretend each team gets a camp each and you fight over the last camp, another fight breaks out, you use your transformation to save you and switch HP all the time and you notice the gift when you finally kill the camp. Getting a gift gives one random item to a person on each team. These items can be truely crap or truely amazing. Note - rapier can be an item here.
Once you've done 2/3 rotations there is a big pause - either fight or dodge, your choice. First to 11 big camps wins, you're done.
Other info -
Grevil camps have truesight. Picking riki and you'll have a bad time.
Do not pick anything squishy, I virtually guarantee you'll lose as you have no source of items and you need to survive while you transform often. If you don't pick tanky, pick disable and mobile. People vs us last night picked some really bad stuff that was mostly agi, we rolled them.
We often just sacrificed camps, you only need to win 2 out of 3 of them a few times, no point in going for a greedy all 3 unless you're experienced and can deal with respawns.
Pudge can hook creeps and steal them at low HP. Body block the hook, respawn timers are low.
Don't use the white default "I have no grevil", its awful. get an egg and fill it with cheap essence (i sell it on the market for 10p each when i have too much - you only need 9).
You can level 1 rosh with any 5 using grevil form. Use blinkbone on grevilform to get in from the dire wide without giving vision. Everyone knew this trick by the end of the night at our difficulty (highest) so just be careful without vision (as i had blink > echoslam, we did some horrible things to people who tried this on us).
If you want to see some example games from me you can see my games on dotabuff.com under Myshra. You'll have to excuse some of the smack talk though, my team like to rile people.